Revert "Simplify making the last statement an expression a return (#500…

…)"

This reverts commit aa45410.

library/src/engine/engine.ts

@@ -203,9 +203,16 @@ export class Engine {
     ctx: RuntimeContext,
     ...argNames: string[]
   ): RuntimeExpressionFunction {
-
-    // Make last statement in an expression a return
-    let userExpression = ctx.value.replace(/([^;\n]*$)/, 'return ($1);')
+    const stmts = ctx.value
+      .split(/;|\n/)
+      .map((s) => s.trim())
+      .filter((s) => s !== '')
+    const lastIdx = stmts.length - 1
+    const last = stmts[lastIdx]
+    if (!last.startsWith('return')) {
+      stmts[lastIdx] = `return (${stmts[lastIdx]});`
+    }
+    let userExpression = stmts.join(';\n').trim()
 
     // Ingore any escaped values
     const escaped = new Map<string, string>()