if( exists $valid_apt_numbers{ $digits_4 } ) {
  $text =~ s{\b($digits_4)\b}{<a href=YADDAYADDA</a>}xmsg;
}

If $digits_4 is defined as in the OP, i.e., as a Regexp object, I don't see how its stringization will ever match any key in %valid_apt_numbers, all of which are "unit" numbers of the format '1001', '2202', etc.

Give a man a fish:  <%-{-{-{-<

In reply to Re^2: Text switching by AnomalousMonk
in thread Text switching by htmanning

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