sub change_punch_process
   {
      my @numbers;
      @q = ("1a", "2b", "3c", "2k");

      foreach ( @q )
      {
         if (/^([0-9]+)/)
         {
            my $exists = 0;
            foreach (@numbers)
            {
               $exists = 1 if ($_ == $1)
            }
            if (!$exists) {push @numbers, $1;}
         }
      }
      print join(",",@numbers);
}

change_punch_process;