Readonly my %VALID_CHAR => ( y => 1, Y => 1, n => 1, N => 1 );
sub continue_yn
  {
   print "Do you wish to continue the installation (Y/N) : ";
   $yn=<STDIN>;
   chomp $yn;

  LOOP:
   while ( 1 )
     {
      last LOOP if $VALID_CHAR{$yn};
      print "Invalid option, please enter an Y or N : ";
      $yn=<STDIN>;
      chomp $yn;
     }

   print "Valid option entered";
  }