The example was fine. It doesn't make sense for logger to need the dualvar.

• If you wanted to pass the error string to the sub, the caller would use "$!".
• If you wanted to pass the error number to sub, the caller would use 0+$!.
• If the sub needs both an error string and an error number, it would take two arguments.
• If the sub wants to look at $!, it wouldn't take it as an argument.