Environment will now accept ':' as temp labels and handle their values accordingly. As soon as a new var is defined, all temp labels are cleared.

src/assembler/env.js

 var PCL = "__PC__";
 
 
+function StoreVar(env, name, val){
+  let initSet = false;
+  if (!(name in Object.keys(env.__vars))){
+    if (env.__parent && env.__parent.hasVar(name))
+      return env.__parent.setVarVal(name, val);
+    initSet = true;
+  }
+  env.__vars[name] = val;
+  if (initSet)
+    env.emitVarVal(name);
+  if (env.__templabels.length > 0){
+    env.__templabels.forEach((l)=>{
+      delete env.__vars[l];
+      delete env.__listeners[l];
+    });
+    env.__templabels = [];
+  }
+}
+
+function StoreTempLabel(env, name, val){
+  env.__vars[name] = val;
+  env.__templabels.push(name);
+  env.emitVarVal(name);
+}
+
+
 class Environment{
   constructor(parent){
     this.__parent = (parent instanceof Environment) ? parent : null;
     this.__vars = {};
     this.__listeners = {};
+
+    this.__templabels = [];
   }
 
   get PC(){return PC;}
       PC = Math.floor(val);
       return this;
     }
-    let initSet = false;
-    if (!(name in Object.keys(this.__vars))){
-      if (this.__parent && this.__parent.hasVar(name))
-        return this.__parent.setVarVal(name, val);
-      initSet = true;
+    if (name === ":"){
+      StoreTempLabel(this, ":" + this.__templabels.length, val);
+    } else {
+      StoreVar(this, name, val);
     }
-    this.__vars[name] = val;
-    if (initSet){
-      this.emitVarVal(name);
+    
     return this;
   }