What host control panel has a "Wildcard DNS" option? Wildcard DNS is something used on DNS servers, not operating systems. Do you mean some DNS hosting service that hosts the domain? Or the Apache configuration? Wildcard DNS basically means any host not defined in the zone is caught by the *.domain.tld entry and sent to that address.

It should be possible host wildcard DNS with Apache. This isn't necessarily a Perl question. You could write a mod_perl module to do the redirection. You may have to do this if there is a complicated lookup for There are likely ways to do it that don't involve Perl. You can even do it that doesn't require a redirect (ie server http://username.domain.tld). Look at mod_rewrite, RedirectMatch, and _default_ vhost.