You don't mention anything about your environment. From the .pl file extension I assume that you are using Perl, but I have no idea which webserver you are using.
If the file asp.pl does not exist, you can create a custom 404 error page to do the redirect. If you are using IIS, this can be accomplished using the IIS management tools.
If the file asp.pl exists, the redirect will have to happen as part of the Perl script in asp.pl, or via some URL rewrite scheme that understands what is and is not valid. If you are using Apache this can be accomplished using .htaccess files. In IIS you may have to insert an ISAPI rewrite module into the server processing stack. For information on doing a redirect in Perl, check this post on perlmonks.
You didn't mention if there were certain query strings that were valid and some that were invalid and should be redirected.
A little more information is required to fully answer your question.