while ($seskey) {
   print "Callsign? or q: \n";

   ( my $call = <STDIN> );

   $call =~ s/[^a-zA-Z0-9]*//g;

   # Should we quit?
   if ( $call =~ m/^q.*/ ) {
         exit;
   }

   if ( not $call =~ m/^[a-zA-Z].*[0-9][a-zA-Z].*$/) {

      system(($^O eq 'MSWin32') ? 'cls' : 'clear');

      print "invalid call \n";

      next;
   }