Your question is a bit unclear. How do you determine whether a given part of the string is equivalent to "H"?

This may be something like what you want:

$thisstring = "abjdkwosyksljadfkjadfaduifalkdjfaslflksdf";

sub H {
  return qr/abjdk|adfkj/;
}

if ($thisstring =~ H) {
  print "Yes!\n";
} else {
  print "No.\n";
}
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