Updated argument count validation

cmd/main.go

@@ -64,7 +64,7 @@ func main() {
 	// 2. Build NFA from postfix representation (Thompson's algorithm)
 	// 3. Run the string against the NFA
 
-	if len(flag.Args()) != 1 { // flag.Args() also strips out program name
+	if len(flag.Args()) < 1 || len(flag.Args()) > 2 { // flag.Args() also strips out program name
 		fmt.Println("ERROR: Missing cmdline args")
 		os.Exit(22)
 	}