$ demo() {
   perl -e'
      use v5.18;
      use Tie::IxHash qw( );
      my %h;
      tie %h, Tie::IxHash:: if $ARGV[0];
      ++$h{ $_ } for "a".."z";
      say keys %h;
   ' -- "$1"
}

$ demo 0
lukphmweqsiorxvnbdfajyczgt

$ demo 0
dpbwuxlvticosyngmrzajefqkh

$ demo 1
abcdefghijklmnopqrstuvwxyz

$ demo 1
abcdefghijklmnopqrstuvwxyz