foreach my $k (@k) {
  $s =~ m/(.)$k(.)/ ;
  if (($1 ne "\0") || ($2 ne "\0")) { delete $h{$k} ; } ;
}

##</code><code>##

for my $k ( @k ) {
    if ( $s =~ /\0$k\0/ ) {
        delete $h{ $k };
        }
    }