diff --git a/hkmc2/jvm/src/test/scala/hkmc2/JSBackendDiffMaker.scala b/hkmc2/jvm/src/test/scala/hkmc2/JSBackendDiffMaker.scala
index 60b605af0..47dac5295 100644
--- a/hkmc2/jvm/src/test/scala/hkmc2/JSBackendDiffMaker.scala
+++ b/hkmc2/jvm/src/test/scala/hkmc2/JSBackendDiffMaker.scala
@@ -109,21 +109,21 @@ abstract class JSBackendDiffMaker extends MLsDiffMaker:
         val (reply, stderr) = host.query(queryStr, !expectRuntimeOrCodeGenErrors && fixme.isUnset && todo.isUnset)
         reply match
           case ReplHost.Result(content, stdout) =>
-            if silent.isUnset then
-              stdout match
-                case None | Some("") =>
-                case Some(str) =>
-                  str.splitSane('\n').foreach: line =>
-                    output(s"> ${line}")
-              content match
-              case "undefined" =>
-              case "null" =>
+            stdout match
+            case None | Some("") =>
+            case Some(str) =>
+              str.splitSane('\n').foreach: line =>
+                output(s"> ${line}")
+            content match
+            case "undefined" =>
+            case "null" =>
+            case _ =>
+              expect.get match
+              case S(expected) if content != expected => raise:
+                ErrorReport(msg"Expected: ${expected}, got: ${content}" -> N :: Nil,
+                  source = Diagnostic.Source.Runtime)
               case _ =>
-                expect.get match
-                  case S(expected) if content != expected => raise:
-                    ErrorReport(msg"Expected: ${expected}, got: ${content}" -> N :: Nil,
-                      source = Diagnostic.Source.Runtime)
-                  case _ => output(s"$prefix= ${content}")
+                if silent.isUnset then output(s"$prefix= ${content}")
           case ReplHost.Empty =>
           case ReplHost.Unexecuted(message) => ???
           case ReplHost.Error(isSyntaxError, message, otherOutputs) =>
@@ -162,7 +162,7 @@ abstract class JSBackendDiffMaker extends MLsDiffMaker:
             if ts.trmImplTree.exists(_.k.isInstanceOf[syntax.ValLike]) => S((nme, ts))
           case _ => N
         case _ => N
-      definedValues.toSeq.sortBy(_._1).foreach: (nme, sym) =>
+      if silent.isUnset then definedValues.toSeq.sortBy(_._1).foreach: (nme, sym) =>
         val le = codegen.Return(codegen.Value.Ref(sym), implct = true)
         val je = nestedScp.givenIn:
           jsb.block(le)
diff --git a/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala b/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
index 72539f36c..2177fc78e 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
@@ -22,7 +22,7 @@ object Elaborator:
     ",",
     "+", "-", "*", "/", "%",
     "==", "!=", "<", "<=", ">", ">=",
-    "===",
+    "===", "!==",
     "&&", "||")
   private val unaryOps = Set("-", "+", "!", "~")
   private val anyOps = Set("super")
diff --git a/hkmc2/shared/src/main/scala/hkmc2/syntax/ParseRule.scala b/hkmc2/shared/src/main/scala/hkmc2/syntax/ParseRule.scala
index 7d28a9e7e..cbb73aa0c 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/syntax/ParseRule.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/syntax/ParseRule.scala
@@ -286,7 +286,11 @@ class ParseRules(using State):
           case (body, _) => Open(body)}*),
     modified(`abstract`, Kw(`class`)(typeDeclBody(Cls))),
     modified(`mut`),
-    modified(`do`),
+    Kw(`do`):
+      ParseRule(s"`do` keyword")(
+        exprOrBlk(ParseRule(s"`do` body")(End(()))):
+          case (body, ()) => Tree.Modified(`do`, N, body)
+        *),
     modified(`virtual`),
     modified(`override`),
     modified(`declare`),
diff --git a/hkmc2/shared/src/main/scala/hkmc2/syntax/Parser.scala b/hkmc2/shared/src/main/scala/hkmc2/syntax/Parser.scala
index 02bf86ff7..78bbc5e1c 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/syntax/Parser.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/syntax/Parser.scala
@@ -580,7 +580,8 @@ abstract class Parser(
         case _ => S(expr(prec))
       Spread(if dotDotDot then Keyword.`...` else Keyword.`..`, S(loc), bod)
     case (tok, loc) :: _ =>
-      TODO(tok)
+      err((msg"Expected an expression; found new line instead" -> S(loc) :: Nil))
+      errExpr
     case Nil =>
       err((msg"Expected an expression; found end of input instead" -> lastLoc :: Nil))
       errExpr
diff --git a/hkmc2/shared/src/test/mlscript-compile/Predef.mjs b/hkmc2/shared/src/test/mlscript-compile/Predef.mjs
index 9804ddb34..0b81c7e0a 100644
--- a/hkmc2/shared/src/test/mlscript-compile/Predef.mjs
+++ b/hkmc2/shared/src/test/mlscript-compile/Predef.mjs
@@ -110,18 +110,33 @@ const Predef$class = class Predef {
       return f5.call(receiver1, ...args);
     };
   } 
-  print(x4) {
+  pass1(f6) {
+    return (...xs) => {
+      return f6(xs[0]) ?? null;
+    };
+  } 
+  pass2(f7) {
+    return (...xs) => {
+      return f7(xs[0], xs[1]) ?? null;
+    };
+  } 
+  pass3(f8) {
+    return (...xs) => {
+      return f8(xs[0], xs[1], xs[2]) ?? null;
+    };
+  } 
+  print(...xs) {
     let tmp;
-    tmp = String(x4);
-    return console.log(tmp) ?? null;
+    tmp = xs.map(String) ?? null;
+    return console.log(...tmp) ?? null;
   } 
-  tupleSlice(xs, i, j) {
+  tupleSlice(xs1, i, j) {
     let tmp;
-    tmp = xs.length - j;
-    return globalThis.Array.prototype.slice.call(xs, i, tmp) ?? null;
+    tmp = xs1.length - j;
+    return globalThis.Array.prototype.slice.call(xs1, i, tmp) ?? null;
   } 
-  tupleGet(xs1, i1) {
-    return globalThis.Array.prototype.at.call(xs1, i1);
+  tupleGet(xs2, i1) {
+    return globalThis.Array.prototype.at.call(xs2, i1);
   } 
   stringStartsWith(string, prefix) {
     return string.startsWith(prefix) ?? null;
diff --git a/hkmc2/shared/src/test/mlscript-compile/Predef.mls b/hkmc2/shared/src/test/mlscript-compile/Predef.mls
index ef863de44..59eac3fbd 100644
--- a/hkmc2/shared/src/test/mlscript-compile/Predef.mls
+++ b/hkmc2/shared/src/test/mlscript-compile/Predef.mls
@@ -15,8 +15,12 @@ fun (.) passTo(receiver, f)(...args) = f(receiver, ...args)
 
 fun (|>.) call(receiver, f)(...args) = f.call(receiver, ...args)
 
-fun print(x) =
-  console.log(String(x))
+fun pass1(f)(...xs) = f(xs.0)
+fun pass2(f)(...xs) = f(xs.0, xs.1)
+fun pass3(f)(...xs) = f(xs.0, xs.1, xs.2)
+
+fun print(...xs) =
+  console.log(...xs.map(String))
 
 val assert = console.assert
 
diff --git a/hkmc2/shared/src/test/mlscript-compile/Str.mjs b/hkmc2/shared/src/test/mlscript-compile/Str.mjs
index dff6c0547..cf22ef318 100644
--- a/hkmc2/shared/src/test/mlscript-compile/Str.mjs
+++ b/hkmc2/shared/src/test/mlscript-compile/Str.mjs
@@ -1,9 +1,12 @@
 const Str$class = class Str {
   constructor() {}
-  concat(a, b) {
+  concat2(a, b) {
     return a + b;
   } 
-  string(value) {
+  concat(...xs) {
+    return xs.join("") ?? null;
+  } 
+  from(value) {
     return globalThis.String(value) ?? null;
   }
   toString() { return "Str"; }
diff --git a/hkmc2/shared/src/test/mlscript-compile/Str.mls b/hkmc2/shared/src/test/mlscript-compile/Str.mls
index 40a5b72cd..ae09f4657 100644
--- a/hkmc2/shared/src/test/mlscript-compile/Str.mls
+++ b/hkmc2/shared/src/test/mlscript-compile/Str.mls
@@ -1,6 +1,10 @@
 
 module Str with ...
 
-fun (~) concat(a, b) = a + b
 
-fun string(value) = globalThis.String(value)
+fun (~) concat2(a, b) = a + b
+
+fun concat(...xs) = xs.join("")
+
+fun from(value) = globalThis.String(value)
+
diff --git a/hkmc2/shared/src/test/mlscript-compile/apps/Accounting.mjs b/hkmc2/shared/src/test/mlscript-compile/apps/Accounting.mjs
index 38945b0eb..b6d459dbf 100644
--- a/hkmc2/shared/src/test/mlscript-compile/apps/Accounting.mjs
+++ b/hkmc2/shared/src/test/mlscript-compile/apps/Accounting.mjs
@@ -39,11 +39,11 @@ class Accounting {
         let scrut, tmp, tmp1, tmp2, tmp3, tmp4;
         scrut = this.balance > 10000;
         if (scrut) {
-          tmp = Str.concat("> **\u2757\uFE0F** Unspent balance of ", this.name);
-          tmp1 = Str.concat(tmp, ": `");
+          tmp = Str.concat2("> **\u2757\uFE0F** Unspent balance of ", this.name);
+          tmp1 = Str.concat2(tmp, ": `");
           tmp2 = this$Accounting.display(this.balance);
-          tmp3 = Str.concat(tmp1, tmp2);
-          tmp4 = Str.concat(tmp3, "`");
+          tmp3 = Str.concat2(tmp1, tmp2);
+          tmp4 = Str.concat2(tmp3, "`");
           return this$Accounting.warnings.push(tmp4) ?? null;
         } else {
           return null;
@@ -64,42 +64,42 @@ class Accounting {
       } 
       wln(txt1) {
         let tmp;
-        tmp = Str.concat(txt1, "\n");
+        tmp = Str.concat2(txt1, "\n");
         return fs.appendFileSync(this.fileName, tmp);
       } 
       init() {
         let tmp, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7, tmp8, tmp9, tmp10, tmp11, tmp12, tmp13;
         tmp = this.wln("");
-        tmp1 = Str.concat("|", "Year");
-        tmp2 = Str.concat(tmp1, "|");
+        tmp1 = Str.concat2("|", "Year");
+        tmp2 = Str.concat2(tmp1, "|");
         tmp3 = this$Accounting.lines.map((x) => {
           return x.name;
         }) ?? null;
         tmp4 = tmp3.join("|") ?? null;
-        tmp5 = Str.concat(tmp2, tmp4);
-        tmp6 = Str.concat(tmp5, "|");
+        tmp5 = Str.concat2(tmp2, tmp4);
+        tmp6 = Str.concat2(tmp5, "|");
         tmp7 = this.wln(tmp6);
-        tmp8 = Str.concat("|", "---");
-        tmp9 = Str.concat(tmp8, "|");
+        tmp8 = Str.concat2("|", "---");
+        tmp9 = Str.concat2(tmp8, "|");
         tmp10 = this$Accounting.lines.map((x) => {
           return "--:";
         }) ?? null;
         tmp11 = tmp10.join("|") ?? null;
-        tmp12 = Str.concat(tmp9, tmp11);
-        tmp13 = Str.concat(tmp12, "|");
+        tmp12 = Str.concat2(tmp9, tmp11);
+        tmp13 = Str.concat2(tmp12, "|");
         return this.wln(tmp13);
       } 
       snapShot(label) {
         let tmp, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6;
         tmp = String(label) ?? null;
-        tmp1 = Str.concat("|", tmp);
-        tmp2 = Str.concat(tmp1, "|");
+        tmp1 = Str.concat2("|", tmp);
+        tmp2 = Str.concat2(tmp1, "|");
         tmp3 = this$Accounting.lines.map((x) => {
           return this$Accounting.display(x.balance);
         }) ?? null;
         tmp4 = tmp3.join("|") ?? null;
-        tmp5 = Str.concat(tmp2, tmp4);
-        tmp6 = Str.concat(tmp5, "|");
+        tmp5 = Str.concat2(tmp2, tmp4);
+        tmp6 = Str.concat2(tmp5, "|");
         return this.wln(tmp6);
       } 
       wrapUp() {
@@ -112,14 +112,14 @@ class Accounting {
         }) ?? null;
         tmp2 = this.wln("### Remaining Available Funds");
         tmp3 = this.wln("");
-        tmp4 = Str.concat("|", "Summary");
-        tmp5 = Str.concat(tmp4, "|   |");
+        tmp4 = Str.concat2("|", "Summary");
+        tmp5 = Str.concat2(tmp4, "|   |");
         tmp6 = this.wln(tmp5);
-        tmp7 = Str.concat("|", "---");
-        tmp8 = Str.concat(tmp7, "|--:|");
+        tmp7 = Str.concat2("|", "---");
+        tmp8 = Str.concat2(tmp7, "|--:|");
         tmp9 = this.wln(tmp8);
-        tmp10 = Str.concat("|", "Matchable");
-        tmp11 = Str.concat(tmp10, "|");
+        tmp10 = Str.concat2("|", "Matchable");
+        tmp11 = Str.concat2(tmp10, "|");
         tmp12 = this$Accounting.lines.filter((x) => {
           return x.isMatchable;
         }) ?? null;
@@ -130,11 +130,11 @@ class Accounting {
           return a + b;
         }, 0);
         tmp15 = this$Accounting.display(tmp14);
-        tmp16 = Str.concat(tmp11, tmp15);
-        tmp17 = Str.concat(tmp16, "|");
+        tmp16 = Str.concat2(tmp11, tmp15);
+        tmp17 = Str.concat2(tmp16, "|");
         tmp18 = this.wln(tmp17);
-        tmp19 = Str.concat("|", "Non-matchable");
-        tmp20 = Str.concat(tmp19, "|");
+        tmp19 = Str.concat2("|", "Non-matchable");
+        tmp20 = Str.concat2(tmp19, "|");
         tmp21 = this$Accounting.lines.filter((x) => {
           return Predef.not(x.isMatchable);
         }) ?? null;
@@ -145,8 +145,8 @@ class Accounting {
           return a + b;
         }, 0);
         tmp24 = this$Accounting.display(tmp23);
-        tmp25 = Str.concat(tmp20, tmp24);
-        tmp26 = Str.concat(tmp25, "|");
+        tmp25 = Str.concat2(tmp20, tmp24);
+        tmp26 = Str.concat2(tmp25, "|");
         return this.wln(tmp26);
       }
       toString() { return "Report(" + this.fileName + ")"; }
@@ -171,7 +171,7 @@ class Accounting {
     tmp1 = report.init() ?? null;
     tmp2 = k(report) ?? null;
     tmp3 = report.wrapUp() ?? null;
-    tmp4 = Str.concat("Report written to ", filename);
+    tmp4 = Str.concat2("Report written to ", filename);
     return Predef.print(tmp4);
   }
   toString() { return "Accounting"; }
diff --git a/hkmc2/shared/src/test/mlscript-compile/apps/CSV.mjs b/hkmc2/shared/src/test/mlscript-compile/apps/CSV.mjs
new file mode 100644
index 000000000..e8063c6a6
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript-compile/apps/CSV.mjs
@@ -0,0 +1,58 @@
+import Str from "./../Str.mjs";
+import Predef from "./../Predef.mjs";
+function CSV(strDelimiter1) { return new CSV.class(strDelimiter1); }
+CSV.class = class CSV {
+  constructor(strDelimiter) {
+    this.strDelimiter = strDelimiter;
+    let tmp, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
+    tmp = this.strDelimiter || ",";
+    this.strDelimiter = tmp;
+    tmp1 = "(\\" + this.strDelimiter;
+    tmp2 = tmp1 + "|\\r?\\n|\\r|^)";
+    tmp3 = "([^\"\\" + this.strDelimiter;
+    tmp4 = tmp3 + "\\r\\n]*))";
+    tmp5 = "(?:\"([^\"]*(?:\"\"[^\"]*)*)\"|" + tmp4;
+    tmp6 = tmp2 + tmp5;
+    tmp7 = new RegExp(tmp6, "gi");
+    this.objPattern = tmp7;
+  }
+  toArrays(strData) {
+    let arrData, arrMatches, scrut, strMatchedDelimiter, scrut1, strMatchedValue, scrut2, tmp, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6;
+    arrData = [
+      []
+    ];
+    tmp7: while (true) {
+      arrMatches = this.objPattern.exec(strData) ?? null;
+      scrut = arrMatches !== null;
+      if (scrut) {
+        strMatchedDelimiter = arrMatches[1];
+        tmp = strMatchedDelimiter != this.strDelimiter;
+        scrut1 = strMatchedDelimiter.length && tmp;
+        if (scrut1) {
+          tmp1 = arrData.push([]) ?? null;
+        } else {
+          tmp1 = null;
+        }
+        scrut2 = arrMatches[2];
+        if (scrut2) {
+          tmp2 = new RegExp("\"\"", "g");
+          tmp3 = arrMatches[2].replace(tmp2, "\"");
+        } else {
+          tmp3 = arrMatches[3];
+        }
+        strMatchedValue = tmp3;
+        tmp4 = arrData.length - 1;
+        tmp5 = arrData.at(tmp4) ?? null;
+        tmp6 = tmp5.push(strMatchedValue) ?? null;
+        continue tmp7;
+      } else {
+        tmp6 = null;
+      }
+      break;
+    }
+    return arrData;
+  }
+  toString() { return "CSV(" + this.strDelimiter + ")"; }
+};
+null
+export default CSV;
diff --git a/hkmc2/shared/src/test/mlscript-compile/apps/CSV.mls b/hkmc2/shared/src/test/mlscript-compile/apps/CSV.mls
new file mode 100644
index 000000000..b8b1250cc
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript-compile/apps/CSV.mls
@@ -0,0 +1,155 @@
+
+// Adapted from https://www.bennadel.com/blog/1504-ask-ben-parsing-csv-strings-with-javascript-exec-regular-expression-command.htm
+// (JS code commented at bottom)
+
+import "../Str.mls"
+open Str
+
+import "../Predef.mls"
+open Predef
+
+
+// The default delimiter is the comma, but this can be overriden here.
+class CSV(strDelimiter) with ...
+
+
+// Check to see if the delimiter is defined. If not, then default to comma.
+set strDelimiter ||= ","
+
+// TODO allow better code layout/formatting
+val objPattern = new RegExp of
+  // Delimiters.
+  "(\\" + strDelimiter + "|\\r?\\n|\\r|^)" +
+    // Quoted fields.
+    "(?:\"([^\"]*(?:\"\"[^\"]*)*)\"|" +
+      // Standard fields.
+      "([^\"\\" + strDelimiter + "\\r\\n]*))"
+  "gi"
+
+// This will parse a delimited string into an array of arrays.
+fun toArrays(strData) =
+  
+  // Create an array to hold our data. Give the array a default empty first row.
+  let arrData = [[]]
+  
+  // Keep looping over the regular expression matches until we can no longer find a match.
+  while
+    let arrMatches = objPattern.exec(strData)
+    arrMatches !== null do
+      
+      // Get the delimiter that was found.
+      let strMatchedDelimiter = arrMatches.1
+      
+      // Check to see if the given delimiter has a length (is not the start of string)
+      // and if it matches field delimiter.
+      // If id does not, then we know that this delimiter is a row delimiter.
+      if strMatchedDelimiter.length && strMatchedDelimiter != strDelimiter do
+        // Since we have reached a new row of data, add an empty row to our data array.
+        arrData.push([])
+      
+      // Now that we have our delimiter out of the way,
+      // let's check to see which kind of value we captured (quoted or unquoted).
+      let strMatchedValue =
+        if arrMatches.2
+        then
+          // We found a quoted value. When we capture this value, unescape any double quotes.
+          arrMatches.2.replace of
+            new RegExp("\"\"", "g")
+            "\""
+        else
+          // We found a non-quoted value.
+          arrMatches.3
+      
+      arrData.at(arrData.length - 1).push(strMatchedValue)
+  
+  arrData
+
+
+/*
+  // This will parse a delimited string into an array of
+  // arrays. The default delimiter is the comma, but this
+  // can be overriden in the second argument.
+  function CSVToArray( strData, strDelimiter ){
+    // Check to see if the delimiter is defined. If not,
+    // then default to comma.
+    strDelimiter = (strDelimiter || ",");
+
+    // Create a regular expression to parse the CSV values.
+    var objPattern = new RegExp(
+      (
+        // Delimiters.
+        "(\\" + strDelimiter + "|\\r?\\n|\\r|^)" +
+
+        // Quoted fields.
+        "(?:\"([^\"]*(?:\"\"[^\"]*)*)\"|" +
+
+        // Standard fields.
+        "([^\"\\" + strDelimiter + "\\r\\n]*))"
+      ),
+      "gi"
+      );
+
+
+    // Create an array to hold our data. Give the array
+    // a default empty first row.
+    var arrData = [[]];
+
+    // Create an array to hold our individual pattern
+    // matching groups.
+    var arrMatches = null;
+
+
+    // Keep looping over the regular expression matches
+    // until we can no longer find a match.
+    while (arrMatches = objPattern.exec( strData )){
+
+      // Get the delimiter that was found.
+      var strMatchedDelimiter = arrMatches[ 1 ];
+
+      // Check to see if the given delimiter has a length
+      // (is not the start of string) and if it matches
+      // field delimiter. If id does not, then we know
+      // that this delimiter is a row delimiter.
+      if (
+        strMatchedDelimiter.length &&
+        (strMatchedDelimiter != strDelimiter)
+        ){
+
+        // Since we have reached a new row of data,
+        // add an empty row to our data array.
+        arrData.push( [] );
+
+      }
+
+
+      // Now that we have our delimiter out of the way,
+      // let's check to see which kind of value we
+      // captured (quoted or unquoted).
+      if (arrMatches[ 2 ]){
+
+        // We found a quoted value. When we capture
+        // this value, unescape any double quotes.
+        var strMatchedValue = arrMatches[ 2 ].replace(
+          new RegExp( "\"\"", "g" ),
+          "\""
+          );
+
+      } else {
+
+        // We found a non-quoted value.
+        var strMatchedValue = arrMatches[ 3 ];
+
+      }
+
+
+      // Now that we have our value string, let's add
+      // it to the data array.
+      arrData[ arrData.length - 1 ].push( strMatchedValue );
+    }
+
+    // Return the parsed data.
+    return( arrData );
+  }
+*/
+
+
diff --git a/hkmc2/shared/src/test/mlscript/apps/CSVTest.mls b/hkmc2/shared/src/test/mlscript/apps/CSVTest.mls
new file mode 100644
index 000000000..0a5e1eaa0
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript/apps/CSVTest.mls
@@ -0,0 +1,40 @@
+:js
+
+import "../../mlscript-compile/apps/CSV.mls"
+
+
+let csv = CSV()
+//│ > CSV {
+//│ >   strDelimiter: ',',
+//│ >   objPattern: /(\,|\r?\n|\r|^)(?:"([^"]*(?:""[^"]*)*)"|([^"\,\r\n]*))/gi
+//│ csv = }
+
+csv.strDelimiter
+//│ = ','
+
+csv.objPattern
+//│ = /(\,|\r?\n|\r|^)(?:"([^"]*(?:""[^"]*)*)"|([^"\,\r\n]*))/gi
+
+csv.toArrays("a,b,c")
+//│ = [ [ 'a', 'b', 'c' ] ]
+
+csv.toArrays("a,b,c\n1,2,3\n4,5,6")
+//│ = [ [ 'a', 'b', 'c' ], [ '1', '2', '3' ], [ '4', '5', '6' ] ]
+
+csv.toArrays("a,b,c\n\n1,2,3\n4,5,6\n")
+//│ > [
+//│ >   [ 'a', 'b', 'c' ],
+//│ >   [ '' ],
+//│ >   [ '1', '2', '3' ],
+//│ >   [ '4', '5', '6' ],
+//│ >   [ '' ]
+//│ = ]
+
+csv.toArrays(",")
+//│ = [ [ '' ] ]
+
+csv.toArrays(",,")
+//│ = [ [ '', '' ] ]
+
+
+
diff --git a/hkmc2/shared/src/test/mlscript/backlog/ToTriage.mls b/hkmc2/shared/src/test/mlscript/backlog/ToTriage.mls
new file mode 100644
index 000000000..0c1ab109f
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript/backlog/ToTriage.mls
@@ -0,0 +1,112 @@
+:js
+:todo
+
+
+// ——— ——— ———
+
+"a" +
+  "b"
+//│ = 'ab'
+
+// FIXME
+"a" +
+  // a
+"b"
+//│ = 'b'
+
+// FIXME
+// :dp
+"a" +
+// a
+"b"
+//│ ╔══[PARSE ERROR] Expected start of statement in this position; found newline instead
+//│ ║  l.20: 	// a
+//│ ║        	    ^
+//│ ║  l.21: 	"b"
+//│ ╙──      	
+
+// ——— ——— ———
+
+true or true
+//│ /!!!\ Uncaught error: scala.MatchError: InfixApp(BoolLit(true),keyword 'or',BoolLit(true)) (of class hkmc2.syntax.Tree$InfixApp)
+
+:fixme
+while false or false do print("ok")
+//│ /!!!\ Uncaught error: scala.MatchError: InfixApp(BoolLit(false),keyword 'or',BoolLit(false)) (of class hkmc2.syntax.Tree$InfixApp)
+
+// ——— ——— ———
+
+let g = [0]
+//│ g = [ 0 ]
+
+:fixme
+set g.0 += 1 // FIXME
+//│ /!!!\ Uncaught error: scala.MatchError: LetLike(keyword 'set',App(Ident(+=),Tup(List(Sel(Ident(g),Ident(0)), IntLit(1)))),None,None) (of class hkmc2.syntax.Tree$LetLike)
+
+:fixme
+set g.0 = g.0 + 1
+//│ > try { let selRes, tmp, tmp1; selRes = this.g[0]; if (selRes === undefined) {   throw new this.Error("Access to required field '0' yielded 'undefined'"); } else {   tmp = selRes; } tmp1 = tmp + 1; this.g.0 = tmp1; null } catch (e) { console.log('\u200B' + e + '\u200B'); }
+//│ >                                                                                                                                                                                                           ^^
+//│ ═══[COMPILATION ERROR] [Uncaught SyntaxError] Unexpected number
+
+// ——— ——— ———
+
+:todo // TODO instrument Predef
+:re
+id(1, 2)
+//│ = 1
+
+// ——— ——— ———
+
+:todo // TODO confusing formatting should not be allowed
+:e
+let x = if true
+then 1
+else 0
+//│ x = 1
+
+// ——— ——— ———
+
+// TODO we should give reasonable meaning to `==`
+//  notably taking into account arrays and data classes;
+//  and deprecated `===` (notably does not work for arrays)
+
+undefined == null
+//│ = true
+
+undefined === null
+//│ = false
+
+// ——— ——— ———
+
+// FIXME not sanitized?
+:ssjs
+Num
+//│ JS:
+//│ this.Num
+
+// ——— ——— ———
+
+Infinity
+//│ = Infinity
+
+:sjs
+val Infinity = 1
+//│ JS (unsanitized):
+//│ this.Infinity = 1; null
+//│ Infinity = Infinity
+
+:sjs
+Infinity
+//│ JS (unsanitized):
+//│ this.Infinity
+//│ = Infinity
+
+module Test with
+  val Infinity = 1
+
+Test.Infinity
+//│ = 1
+
+// ——— ——— ———
+
diff --git a/hkmc2/shared/src/test/mlscript/backlog/UCS.mls b/hkmc2/shared/src/test/mlscript/backlog/UCS.mls
new file mode 100644
index 000000000..e9c48312b
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript/backlog/UCS.mls
@@ -0,0 +1,97 @@
+:js
+:todo
+
+
+// ——— ——— ———
+
+:fixme
+while
+    let arrMatches = true
+    arrMatches
+  do
+    print(arrMatches)
+//│ /!!!\ Uncaught error: scala.MatchError: InfixApp(IfLike(keyword 'while',None,Block(List(LetLike(keyword 'let',Ident(arrMatches),Some(BoolLit(true)),None), Ident(arrMatches)))),keyword 'do',Block(List(App(Ident(print),Tup(List(Ident(arrMatches))))))) (of class hkmc2.syntax.Tree$InfixApp)
+
+// ——— ——— ———
+
+let arrMatches = ()
+
+// * Note: produces a match error
+:fixme
+if
+  arrMatches !== null
+  do
+    ()
+//│ ═══[ERROR] Unrecognized term split (null).
+//│ ═══[RUNTIME ERROR] Error: match error
+
+// * This one works:
+if
+  arrMatches !== null do
+    ()
+
+// ——— ——— ———
+
+:fixme
+if
+  true and
+  true do
+    print("ok")
+//│ /!!!\ Uncaught error: scala.NotImplementedError: an implementation is missing
+
+if
+  true and
+    true do
+      print("ok")
+//│ > ok
+
+:fixme
+if
+  true
+  and
+  true do
+    print("ok")
+//│ /!!!\ Uncaught error: scala.NotImplementedError: an implementation is missing
+
+if
+  true
+  and true do
+    print("ok")
+//│ > ok
+
+if
+  true
+  and true
+  and true do
+    print("ok")
+//│ > ok
+
+:fixme
+if
+  true
+  and true
+  let x = 1
+  and true do
+    print("ok")
+//│ /!!!\ Uncaught error: scala.MatchError: InfixApp(InfixApp(IntLit(1),keyword 'and',BoolLit(true)),keyword 'do',Block(List(App(Ident(print),Tup(List(StrLit(ok))))))) (of class hkmc2.syntax.Tree$InfixApp)
+
+// ——— ——— ———
+
+let audits = new Set()
+//│ audits = Set(0) {}
+
+:fixme
+if audits.has(1) === true do
+  print("ok")
+else 
+  1
+//│ ╔══[ERROR] The following branches are unreachable.
+//│ ╟── Because the previous split is full.
+//│ ║  l.84: 	if audits.has(1) === true do
+//│ ║        	   ^^^^^^^^^^^^^^^^^^^^^^^^^
+//│ ║  l.85: 	  print("ok")
+//│ ╙──      	^^^^^^^^^^^^^
+//│ = 1
+
+// ——— ——— ———
+
diff --git a/hkmc2/shared/src/test/mlscript/basics/PredefTest.mls b/hkmc2/shared/src/test/mlscript/basics/PredefTest.mls
index c09f0f1cb..dea0b142e 100644
--- a/hkmc2/shared/src/test/mlscript/basics/PredefTest.mls
+++ b/hkmc2/shared/src/test/mlscript/basics/PredefTest.mls
@@ -35,3 +35,7 @@ new Predef.Test
 //│ ═══[RUNTIME ERROR] Error: Access to required field 'x' yielded 'undefined'
 
 
+print(1, 2, 3)
+//│ > 1 2 3
+
+
diff --git a/hkmc2/shared/src/test/mlscript/basics/StrTest.mls b/hkmc2/shared/src/test/mlscript/basics/StrTest.mls
new file mode 100644
index 000000000..c0edf0b59
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript/basics/StrTest.mls
@@ -0,0 +1,55 @@
+:js
+
+import "../../mlscript-compile/Str.mls"
+
+open Str
+
+
+concat of "a", "b", "c"
+//│ = 'abc'
+
+concat of
+  "a"
+  "b"
+  "c"
+//│ = 'abc'
+
+
+// TODO (~) should be sanitized
+
+(~)("a", "b", "c")
+//│ = 'ab'
+
+(~)("a")
+//│ = 'a'
+
+~"a"
+//│ = 'a'
+
+:w
+~("a", "b")
+//│ ╔══[WARNING] Pure expression in statement position
+//│ ║  l.30: 	~("a", "b")
+//│ ╙──      	  ^^^
+//│ = 'b'
+
+:pe
+~ of "a", "b"
+//│ ╔══[PARSE ERROR] Expected start of statement in this position; found 'of' keyword instead
+//│ ║  l.37: 	~ of "a", "b"
+//│ ╙──      	  ^^
+//│ ╔══[PARSE ERROR] Expected end of input; found literal instead
+//│ ║  l.37: 	~ of "a", "b"
+//│ ╙──      	     ^^^
+
+(~) of "a", "b"
+//│ = 'ab'
+
+
+fun test(...xs) =
+  concat of ...xs, "!"
+
+test("a", "b", "c")
+//│ = 'abc!'
+
+
diff --git a/hkmc2/shared/src/test/mlscript/basics/WeirdCalls.mls b/hkmc2/shared/src/test/mlscript/basics/WeirdCalls.mls
new file mode 100644
index 000000000..8e92d728c
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript/basics/WeirdCalls.mls
@@ -0,0 +1,75 @@
+:js
+
+
+// TODO: should report that such `print` reference does not do anything in statement position
+print
+(
+  "A"
+)
+//│ = 'A'
+
+:fixme
+print
+  (
+    "A"
+  )
+//│ ╔══[ERROR] Illegal juxtaposition right-hand side.
+//│ ║  l.14: 	    "A"
+//│ ╙──      	    ^^^
+//│ = [Function: print]
+
+:pe
+print of
+(
+  "A"
+)
+//│ ╔══[PARSE ERROR] Expected an expression; found new line instead
+//│ ║  l.22: 	print of
+//│ ║        	        ^
+//│ ║  l.23: 	(
+//│ ╙──      	
+
+:pe
+print of
+("A")
+//│ ╔══[PARSE ERROR] Expected an expression; found new line instead
+//│ ║  l.33: 	print of
+//│ ║        	        ^
+//│ ║  l.34: 	("A")
+//│ ╙──      	
+
+print of
+  (
+    "A"
+  )
+//│ > A
+
+:pe
+print of
+  (
+    "A"
+)
+//│ ╔══[PARSE ERROR] Mistmatched closing indentation
+//│ ║  l.50: 	    "A"
+//│ ║        	       ^
+//│ ║  l.51: 	)
+//│ ║        	
+//│ ╟── does not correspond to opening parenthesis
+//│ ║  l.49: 	  (
+//│ ╙──      	  ^
+//│ ╔══[PARSE ERROR] Unexpected closing parenthesis
+//│ ║  l.51: 	)
+//│ ╙──      	^
+//│ > A
+
+print of (
+  "A"
+)
+//│ > A
+
+print(
+  "A"
+)
+//│ > A
+
+
diff --git a/hkmc2/shared/src/test/mlscript/codegen/Do.mls b/hkmc2/shared/src/test/mlscript/codegen/Do.mls
index cd7759be9..523c491b3 100644
--- a/hkmc2/shared/src/test/mlscript/codegen/Do.mls
+++ b/hkmc2/shared/src/test/mlscript/codegen/Do.mls
@@ -20,18 +20,32 @@ do 1
 //│ ║  l.18: 	do 1
 //│ ╙──      	   ^
 
+do
+  let hello = 1
+  ()
+
+// FIXME shouldn't be accessible
+:todo
+:re
+print(globalThis.hello)
+//│ > 1
+
 :ucs desugared
 val f = case
   0 then "null"
   do console.log("non-null")
   1 then "unit"
-  _ then "other"
+  let res = "other"
+  do print(res)
+  _ then res
 //│ Desugared:
 //│ >  if
 //│ >    caseScrut is 0 then "null"
 //│ >    let $doTemp = globalThis:import#Prelude#666(.)console‹member:console›(.)log("non-null")
 //│ >    caseScrut is 1 then "unit"
-//│ >    else "other"
+//│ >    let res = "other"
+//│ >    let $doTemp = member:Predef#666(.)print‹member:print›(res#666)
+//│ >    else res#666
 //│ f = [Function: tmp]
 
 f(0)
@@ -43,5 +57,7 @@ f(1)
 
 f(2)
 //│ > non-null
+//│ > other
 //│ = 'other'
 
+
diff --git a/hkmc2/shared/src/test/mlscript/codegen/GlobalThis.mls b/hkmc2/shared/src/test/mlscript/codegen/GlobalThis.mls
index f99b0fe27..877cefcdd 100644
--- a/hkmc2/shared/src/test/mlscript/codegen/GlobalThis.mls
+++ b/hkmc2/shared/src/test/mlscript/codegen/GlobalThis.mls
@@ -2,7 +2,7 @@
 
 
 :silent
-globalThis
+let g = globalThis
 
 
 // FIXME prevent rebinding of this name
diff --git a/hkmc2/shared/src/test/mlscript/decls/Prelude.mls b/hkmc2/shared/src/test/mlscript/decls/Prelude.mls
index 4b8658f03..10f50b438 100644
--- a/hkmc2/shared/src/test/mlscript/decls/Prelude.mls
+++ b/hkmc2/shared/src/test/mlscript/decls/Prelude.mls
@@ -8,9 +8,11 @@ declare class Bool
 declare class Int
 declare class Num
 declare class Str
+declare class Set
 declare class Error(msg)
 
 declare class String
+declare class RegExp
 
 // declare module Math // TODO: list members
 declare val Math // so we can, eg, `open { pow }` in the meantime
@@ -18,6 +20,7 @@ declare val Math // so we can, eg, `open { pow }` in the meantime
 declare val console
 declare val process
 declare val fs
+declare val Infinity
 
 
 declare module Predef with
diff --git a/hkmc2/shared/src/test/mlscript/interop/Array.mls b/hkmc2/shared/src/test/mlscript/interop/Array.mls
new file mode 100644
index 000000000..13a01bbf7
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript/interop/Array.mls
@@ -0,0 +1,38 @@
+:js
+
+
+let arr = [true, false]
+//│ arr = [ true, false ]
+
+
+// * Array methods annoyingly supply extra arguments, such as the index and the array itself
+:re
+arr.map(_ === false)
+//│ ═══[RUNTIME ERROR] Error: Function expected 1 arguments but got 3
+
+:todo
+arr.map((e, ...) => e === false)
+//│ /!!!\ Uncaught error: scala.MatchError: Spread(keyword '...',Some(Loc(12,15,Array.mls:+14)),None) (of class hkmc2.syntax.Tree$Spread)
+
+arr.map(pass1(_ === false))
+//│ = [ false, true ]
+
+
+[1,3,2].map((x, _, _) => x + 1).sort()
+//│ = [ 2, 3, 4 ]
+
+:fixme
+[1,3,2].map((x, _, _) => x + 1)
+  .sort()
+//│ ╔══[PARSE ERROR] Expected an expression; found new line instead
+//│ ║  l.26: 	  .sort()
+//│ ╙──      	  ^^^^^
+//│ ╔══[PARSE ERROR] Unexpected selector here
+//│ ║  l.26: 	  .sort()
+//│ ╙──      	  ^^^^^
+//│ ╔══[ERROR] Illegal juxtaposition right-hand side.
+//│ ║  l.26: 	  .sort()
+//│ ╙──      	  ^^^^^
+//│ = [ 2, 4, 3 ]
+
+
diff --git a/hkmc2/shared/src/test/mlscript/interop/Number.mls b/hkmc2/shared/src/test/mlscript/interop/Number.mls
new file mode 100644
index 000000000..e1082dd9c
--- /dev/null
+++ b/hkmc2/shared/src/test/mlscript/interop/Number.mls
@@ -0,0 +1,15 @@
+:js
+
+
+
+globalThis.Number("0.50")
+//│ = 0.5
+
+
+:fixme
+let num = _ globalThis.Number()
+//│ ═══[ERROR] Illegal position for '_' placeholder.
+
+
+
+
diff --git a/hkmc2/shared/src/test/mlscript/parser/Of.mls b/hkmc2/shared/src/test/mlscript/parser/Of.mls
index 399b480cd..1d81d1c56 100644
--- a/hkmc2/shared/src/test/mlscript/parser/Of.mls
+++ b/hkmc2/shared/src/test/mlscript/parser/Of.mls
@@ -77,6 +77,13 @@ of 1
 :fixme
 print of 
 123
-//│ /!!!\ Uncaught error: scala.NotImplementedError: NEWLINE (of class NEWLINE$)
+//│ ╔══[PARSE ERROR] Expected an expression; found new line instead
+//│ ║  l.78: 	print of 
+//│ ║        	         ^
+//│ ║  l.79: 	123
+//│ ╙──      	
+//│ Parsed:
+//│ 	App(Ident(print),Tup(List(Error())))
+//│ 	IntLit(123)
 
 
diff --git a/hkmc2/shared/src/test/mlscript/ucs/examples/EitherOrBoth.mls b/hkmc2/shared/src/test/mlscript/ucs/examples/EitherOrBoth.mls
index 71b517f9d..9f9619e5c 100644
--- a/hkmc2/shared/src/test/mlscript/ucs/examples/EitherOrBoth.mls
+++ b/hkmc2/shared/src/test/mlscript/ucs/examples/EitherOrBoth.mls
@@ -73,6 +73,6 @@ fun isBoth[A, B](eob: EitherOrBoth[A, B]): Bool =
 
 fun eobToString[A, B](eob: EitherOrBoth[A, B]): Str =
   if eob is
-    Left(left) then "Left(" ~ string(left) ~ ")"
-    Right(right) then "Right(" ~ string(right) ~ ")"
-    Both(left, right) then "Both(" ~ string(left) ~ ", " ~ string(right) ~ ")"
+    Left(left) then "Left(" ~ Str.from(left) ~ ")"
+    Right(right) then "Right(" ~ Str.from(right) ~ ")"
+    Both(left, right) then "Both(" ~ Str.from(left) ~ ", " ~ Str.from(right) ~ ")"
diff --git a/hkmc2/shared/src/test/mlscript/ucs/examples/ListFold.mls b/hkmc2/shared/src/test/mlscript/ucs/examples/ListFold.mls
index edbde8138..3a4f3b50e 100644
--- a/hkmc2/shared/src/test/mlscript/ucs/examples/ListFold.mls
+++ b/hkmc2/shared/src/test/mlscript/ucs/examples/ListFold.mls
@@ -24,10 +24,10 @@ fun join(sep) =
   fun aux(acc, xs) =
     if xs is
       Nil then acc
-      Cons(x, xs') then aux(acc ~ sep ~ string(x), xs')
+      Cons(x, xs') then aux(acc ~ sep ~ Str.from(x), xs')
   (xs) =>
     if xs is
-      Cons(x, xs') then aux(string(x), xs')
+      Cons(x, xs') then aux(Str.from(x), xs')
       Nil then ""
 
 join(", ")(1 :: 2 :: 3 :: Nil)
diff --git a/hkmc2/shared/src/test/mlscript/ucs/examples/Permutations.mls b/hkmc2/shared/src/test/mlscript/ucs/examples/Permutations.mls
index 0f11085ce..c81261579 100644
--- a/hkmc2/shared/src/test/mlscript/ucs/examples/Permutations.mls
+++ b/hkmc2/shared/src/test/mlscript/ucs/examples/Permutations.mls
@@ -23,10 +23,10 @@ fun join(sep) =
   fun aux(acc, xs) =
     if xs is
       Nil then acc
-      Cons(x, xs') then aux(acc ~ sep ~ string(x), xs')
+      Cons(x, xs') then aux(acc ~ sep ~ Str.from(x), xs')
   (xs) =>
     if xs is
-      Cons(x, xs') then aux(string(x), xs')
+      Cons(x, xs') then aux(Str.from(x), xs')
       Nil then ""
 fun showList(xs) = "[" ~ join(", ")(xs) ~ "]"
 fun foldLeft(f)(z) =
diff --git a/out/apps/comp3031-fall24.md b/out/apps/comp3031-fall24.md
new file mode 100644
index 000000000..f957e827f
--- /dev/null
+++ b/out/apps/comp3031-fall24.md
@@ -0,0 +1,42 @@
+# Grades
+
+| # | id | uid | score | grade | name |
+|---|---|---:|---|---|---|
+| 1| 21064231| yhliaf | 98.88 | A+ | LI, Yu Hong Harry |
+| 2| 20966509| ltching | 98.05 | A+ | CHING, Long Tin |
+| 3| 20950108| hlyual | 94.55 | A+ | YU, Hon Lam |
+| 4| 20844646| qduanaa | 93 | A+ | DUAN, Qinkai |
+| 5| 20824086| yharimoto | 91 | A+ | HARIMOTO, Yuken |
+| 6| 20992302| tkorganbayev | 84.75 | A | KORGANBAYEV, Taimas |
+| 7| 20965646| scyeungaf | 82.35 | A | YEUNG, Sin Chun |
+| 8| 20949965| cnleungaf | 81.9 | A | LEUNG, Cheuk Nang |
+| 9| 21160047| rblazek | 81.83 | A | BLAZEK, Richard |
+| 10| 20988222| rbaishuak | 81.1 | A | BAISHUAK, Raiymbek |
+| 11| 20963258| kytsuiad | 76.93 | B+ | TSUI, Ka Yi |
+| 12| 21010747| bsakenov | 74.95 | B+ | SAKENOV, Batyrkhan |
+| 13| 20759023| orbhandari | 74.9 | B+ | BHANDARI, Om Raj |
+| 14| 21022180| msakhmoldin | 74.9 | B+ | SAKHMOLDIN, Mukhammadarif |
+| 15| 20493849| zzhangcy | 74.7 | B | ZHANG, Zidi |
+| 16| 20944264| ygubb | 73.35 | B | GU, Yuyang |
+| 17| 20726313| hhpark | 71.78 | B | PARK, Hyun Hu |
+| 18| 20862296| ttchui | 69.68 | AU | CHUI, Tsz Tou |
+| 19| 20920921| cmcheungaj | 65.4 | B | CHEUNG, Cheuk Man |
+| 20| 21161596| rdgao | 63.1 | B | GAO, Richard Daniel |
+| 21| 20862105| lklamad | 62.88 | B | LAM, Leung Kin |
+| 22| 20957065| thkwokah | 61.75 | B | KWOK, Tsz Hin |
+| 23| 20964563| yliner | 59.25 | C+ | LIN, Yi |
+| 24| 20855956| tykongab | 57.5 | C+ | KONG, Tsz Yui |
+| 25| 20853087| hflamag | 56 | C+ | LAM, Hung Fai |
+| 26| 21160059| kajoyce | 51.93 | C+ | JOYCE, Kitty Amelia |
+| 27| 20966303| kclambd | 49.23 | C | LAM, King Cheuk |
+| 28| 20860200| ynwongaf | 46.25 | C | WONG, Yin Nok |
+| 29| 20825676| suryanarayan | 42 | C | SURYA-NARAYAN, . |
+| 30| 20865169| lcman | 41.33 | D | MAN, Lai Chuen |
+| 31| 20817514| ghanab | 39.8 | D | HAN, Gyungchae |
+| 32| 21066552| ksngah | 38.48 | D | NG, King Sum |
+| 33| 20759566| yzhongbd | 33.33 | F | ZHONG, Yingqi |
+| 34| 20855449| sltong | 26.25 | F | TONG, Sui Lam |
+| 35| 20803288| mytoab | 22.38 | F | TO, Ming Yan |
+| 36| 20855023| phtaiaa | 2.25 | F | TAI, Pui Hong |
+| 37| 21039767| hbaeaa | 0 | F | BAE, Hangyeol |
+| 38| 21160853| mmehari | 0 | F | MEHARI, Mathias |