$recipient = 'test@test.edu' if ($FORM{'ckusno'});

##</code><code>##

$recipient2 = 'test@test.edu';

sub mail_it {
   my ($to) = @_;

   open (MAIL, "|$mailprog $to") || die "Can't open $mailprog!\n";
   print MAIL "Reply-to: $FORM{'espr2'} $FORM{'estb'} $FORM{'espr'}\n";
   print MAIL "MIME-Version: 1.0\n";
   print MAIL "To: $to\n";
   ...
   print MAIL "</body></html>";
   close (MAIL);
}

mail_it($receipient);
mail_it($receipient2) if ($FORM{'ckusno'});