my $width = 80;
           sub process { ... }
           GetOptions ('width=i' => \$width, '<>' => \&process);

       When applied to the following command line:

           arg1 --width=72 arg2 --width=60 arg3

       This will call "process("arg1")" while "$width" is "80",
       "process("arg2")" while "$width" is "72", and
       "process("arg3")" while "$width" is "60".