diff --git a/src/threads.js b/src/threads.js
index 1b0db94b..1b2fc017 100644
--- a/src/threads.js
+++ b/src/threads.js
@@ -7506,10 +7506,9 @@ VariableFrame.prototype.allNames = function (upTo, includeHidden) {
 function JSCompiler(aProcess) {
 	this.process = aProcess;
 	this.source = null; // a context
- 	this.gensyms = new Map(); // temp dictionary for parameter substitutions
+ 	this.gensyms = null; // temp dictionary for parameter substitutions
   	this.implicitParams = null;
    	this.paramCount = null;
-    this.scriptVarCounter = null;
 }
 
 JSCompiler.prototype.toString = function () {
@@ -7519,19 +7518,12 @@ JSCompiler.prototype.toString = function () {
 JSCompiler.prototype.compileFunction = function (aContext, implicitParamCount) {
     var block = aContext.expression,
   		parameters = aContext.inputs,
+        parms = [],
         hasEmptySlots = false,
-        plength = 0;
+        i;
 
 	this.source = aContext;
-    if (implicitParamCount == null || implicitParamCount === '') {
-        this.implicitParams = 1;
-    } else {
-        this.implicitParams = implicitParamCount >> 0;
-        if (this.implicitParams < 0) {
-            // use 1 if implicitParamCount doesn't make sense
-            this.implicitParams = 1;
-        }
-    }
+    this.implicitParams = implicitParamCount || 1;
 
 	// scan for empty input slots
  	hasEmptySlots = !isNil(detect(
@@ -7540,7 +7532,7 @@ JSCompiler.prototype.compileFunction = function (aContext, implicitParamCount) {
     ));
 
     // translate formal parameters into gensyms
-    this.gensyms.clear();
+    this.gensyms = new Map();
     this.paramCount = 0;
     if (parameters.length) {
         // test for conflicts
@@ -7553,34 +7545,33 @@ JSCompiler.prototype.compileFunction = function (aContext, implicitParamCount) {
         }
         // map explicit formal parameters
         parameters.forEach((pName, idx) => {
-        	this.gensyms.set(pName, 'p[' + idx + ']');
+        	var pn = 'p' + idx;
+            parms.push(pn);
+        	this.gensyms.set(pName, pn);
         });
-        plength = parameters.length;
     } else if (hasEmptySlots) {
-    	plength = this.implicitParams;
-    }   
+    	if (this.implicitParams > 1) {
+        	for (i = 0; i < this.implicitParams; i += 1) {
+         		parms.push('p' + i);
+         	}
+     	} else {
+        	// allow for a single implicit formal parameter
+        	parms = ['p0'];
+        }
+    }
 
     // compile using gensyms
 
-    this.scriptVarCounter = 0;
-    var code = 'proc=p.pop();\n';
-    if (plength) {
-        // fill missing parameters with empty string
-        code += 'while(' + plength + '>p.length)p.push("");\n';
-    }
     if (block instanceof CommandBlockMorph) {
-        code += this.compileSequence(block) + 'return ""';
-    } else {
-        code += 'return ' + this.compileExpression(block);
+        return Function.apply(
+            null,
+            parms.concat([this.compileSequence(block)])
+        );
     }
-    block = 'var ';
-    this.gensyms.forEach(function (value) {
-        if (value.charAt(0) === 's') {
-            // declare script variable 
-            block += value + '=0,';
-        }
-    });
-    return Function('...p', block + code);
+    return Function.apply(
+        null,
+        parms.concat(['return ' + this.compileExpression(block)])
+    );
 };
 
 JSCompiler.prototype.compileExpression = function (block) {
@@ -7615,49 +7606,21 @@ JSCompiler.prototype.compileExpression = function (block) {
     case 'evaluate':
         return 'invoke(' +
             this.compileInput(inputs[0]) +
-            ', ' +
+            ',' +
             this.compileInput(inputs[1]) +
             ')';
 
     // special command forms
-    case 'doDeclareVariables':
-        block = '';
-        inputs[0].inputs().forEach(({children: {0: {blockSpec: name}}}) => {
-            if (gensym = this.gensyms.get(name)) {
-                // we already have that script variable, just set it to 0
-                block += gensym + '=';
-                return;
-            }
-            var gensym = 's' + this.scriptVarCounter++;
-            block += gensym + '=';
-            this.gensyms.set(name, gensym);
-        });
-        return block + '0';
-    case 'reportGetVar':
-        return this.gensyms.get(block.blockSpec) || ('proc.getVarNamed("' +
-            this.escape(block.blockSpec) +
-            '")');
-    case 'doSetVar':
-        if (inputs[0] instanceof ArgMorph && (target = this.gensyms.get(inputs[0].evaluate()))) {
-            // setting gensym (script or argument) variable
-            return target + ' = ' + this.compileInput(inputs[1]);
-        }
-        // redirect var to process
-        return 'proc.setVarNamed(' +
+    case 'doSetVar': // redirect var to process
+        return 'arguments[arguments.length - 1].setVarNamed(' +
             this.compileInput(inputs[0]) +
-            ', ' +
+            ',' +
             this.compileInput(inputs[1]) +
             ')';
-    case 'doChangeVar':
-        if (inputs[0] instanceof ArgMorph && (target = this.gensyms.get(inputs[0].evaluate()))) {
-            return '{const d=' + this.compileInput(inputs[1]) +
-                ',v=parseFloat(' + target + ');' +
-                target + '=isNaN(v)?d:v+parseFloat(d)}';
-        }
-        // redirect var to process
-        return 'proc.incrementVarNamed(' +
+    case 'doChangeVar': // redirect var to process
+        return 'arguments[arguments.length - 1].incrementVarNamed(' +
             this.compileInput(inputs[0]) +
-            ', ' +
+            ',' +
             this.compileInput(inputs[1]) +
             ')';
     case 'doReport':
@@ -7676,9 +7639,7 @@ JSCompiler.prototype.compileExpression = function (block) {
             '} else {\n' +
             this.compileSequence(inputs[2].evaluate()) +
             '}';
-    case 'reportBoolean':
-    case 'reportNewList':
-        return this.compileInput(inputs[0]);
+
     default:
         target = this.process[selector] ? this.process
             : (this.source.receiver || this.process.receiver);
@@ -7687,11 +7648,13 @@ JSCompiler.prototype.compileExpression = function (block) {
         if (isSnapObject(target)) {
             if (rcvr === 'SpriteMorph.prototype') {
                 // fix for blocks like (x position)
-                rcvr = 'proc.blockReceiver()';
+                rcvr = 'arguments[arguments.length - 1].blockReceiver()';
             } 
-            return rcvr + '.' + selector + '(' + args + ')';
+            return rcvr + '.' + selector + '(' + args +')';
         } else {
-            return 'proc.' + selector + '(' + args + ')';
+            return 'arguments[arguments.length - 1].' +
+                selector +
+                '(' + args + ')';
         }
     }
 };
@@ -7706,13 +7669,13 @@ JSCompiler.prototype.compileSequence = function (commandBlock) {
 
 JSCompiler.prototype.compileInfix = function (operator, inputs) {
     return '(' + this.compileInput(inputs[0]) + ' ' + operator + ' ' +
-        this.compileInput(inputs[1]) + ')';
+        this.compileInput(inputs[1]) +')';
 };
 
 JSCompiler.prototype.compileInputs = function (array) {
     var args = '';
     array.forEach(inp => {
-        if (args) {
+        if (args.length) {
             args += ', ';
         }
         args += this.compileInput(inp);
@@ -7728,7 +7691,7 @@ JSCompiler.prototype.compileInput = function (inp) {
         if (this.implicitParams > 1) {
          	if (this.paramCount < this.implicitParams) {
             	this.paramCount += 1;
-             	return 'p[' + (this.paramCount - 1) + ']';
+             	return 'p' + (this.paramCount - 1);
         	}
             throw new Error(
                 localize('expecting') + ' ' + this.implicitParams + ' '
@@ -7736,7 +7699,7 @@ JSCompiler.prototype.compileInput = function (inp) {
                     + this.paramCount
             );
         }
-		return 'p[0]';
+		return 'p0';
     } else if (inp instanceof MultiArgMorph) {
         return 'new List([' + this.compileInputs(inp.inputs()) + '])';
     } else if (inp instanceof ArgLabelMorph) {
@@ -7765,6 +7728,16 @@ JSCompiler.prototype.compileInput = function (inp) {
             );
         }
     } else if (inp instanceof BlockMorph) {
+        if (inp.selector === 'reportGetVar') {
+        	if (this.gensyms.has(inp.blockSpec)) {
+            	// un-quoted gensym:
+            	return this.gensyms.get(inp.blockSpec);
+        	}
+         	// redirect var query to process
+            return 'arguments[arguments.length - 1].getVarNamed("' +
+            	this.escape(inp.blockSpec) +
+            	'")';
+        }
         return this.compileExpression(inp);
     } else {
         throw new Error(