Did you forget to configure your mail client to remove mail from the POP3 server after it has been downloaded? Maybe you didn't notice for a few weeks, and you want a quick way to get rid of the accumulated mess. No big deal with
Net::POP3. It's not as flavorful as Mail::POP3Client, but good enough for this task. Bonus: it's a Perl 5.8 core module.
#!/usr/bin/perl
use warnings;
use strict;
use Net::POP3;
my $pop = Net::POP3->new('your.pop3server.com')
or die "Net::POP3 new failed";
my $msgs = $pop->login('username', 'password')
or die "Login failed - check the user/pass";
print "Deleting $msgs messages from POP3 server\n";
$pop->delete($_) or die "Failed to delete msgnum $_"
for (1..$msgs);
$pop->quit;