Implement assign and set commands, improve output format

src/vm/lexer.ts

@@ -17,6 +17,9 @@ const LITERAL_MAP: Record<string, string> = {
     's': ' ',
 }
 
+export const tokenIsLVal = (input: LexInput): boolean =>
+    !input.literal && !!input.value.match(/^\$[a-zA-Z0-9_]+$/)
+
 export class Lexer extends BehaviorSubject<LexToken> {
     private isEscape: boolean = false
     private inQuote?: '"'|"'"