OK, I think the problem is the accountAD ie the email address includes a @ character which needs escaping when you use it in a URL

sub email {

my $accountAD = CGI::escape( "$form{'usermail'}" ); ## here

open (MAIL, "|$sendmail -t") or die "Cannot access mail";
  print MAIL "To: $form{'usermail'}\n";
  print MAIL "From: $adminmail\n";
  print MAIL "Subject: Verify your Email Address\n\n";
  print MAIL "http://sulfericacid.perlmonk.org/evs/revised.pl?accountI
+D=$accountID&accountAD=$accountAD\n";
close (MAIL);
}
[download]

poj