I really don't use Getopt::Long very often, but the docs seemed pretty clear to me...

     = type [ desttype ]
         The option requires an argument of the given type.
         Supported types are:

         s   String. An arbitrary sequence of characters. It is
             valid for the argument to start with "-" or "--".
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If you want your debug option to take an optional argument, you can specify that with a colon instead of an equals; i.e. 'debug:s' rather than 'debug=s'.

How do people cope when writing a a Perl wrapper which accepts known & unkwon options for the wrapped program?

Have you looked at how to use Getopt::Long::Configure() to configure Getopt::Long's behavior? It seems that you can use Getopt::Long::Configure('pass_through') to tell Getopt::Long to leave unknown options in @ARGV. You might want to use it with Getopt::Long::Configure('require_order') or Getopt::Long::Configure('permute') as well.

-sauoq
"My two cents aren't worth a dime.";