Handle unknown command line option

_web_server/playground-server.scm

@@ -459,11 +459,17 @@
           (vvp (string-trim (or (option-get opts "vvp-exe") "vvp")))
           (iverilog (string-trim (or (option-get opts "iverilog-exe") "iverilog"))))
 
-      (if (option-get opts "help")
-          (begin
+      (cond
+       (err
+        (display (format "Unknown option '~a'\n" err))
         (print-help (car args))
         (exit -1))
-          (begin
+
+       ((option-get opts "help")
+        (print-help (car args))
+        (exit -1))
+
+       (else
         (printlog "Listen on '~a' port '~a'" addr port)
         (printlog "Server URL: '~a/~a'" host root)