Expanding on what tye said, you are wandering in very dangerous territory with your construct. First of all your construct is wandering into the my $foo if 0 bug. Secondly if your user mistypes the command line ever so slightly then neither you nor they get a chance to catch that fact. Thirdly you do not have any chance to choose to have certain options take arguments.

I generally rectify all of these with Getopt::Std. If you want longer option names, you can use Getopt::Long instead. (It has a significantly more complex interface though.) Both are part of the standard distribution..