##
$regExpKey = (^\#!/usr/bin/perl[^\n]*\n)
$searchPattern = (^\#!/usr/bin/perl[^\n]*\n)
$replacementPattern = ${^MATCH}\x0Ause English \( no_match_vars \);\x0A
####
$content =~ s{$searchPattern}{${^MATCH}$replacementPattern}gxms;
####
"
${^MATCH}\x0Ause English \( no_match_vars \);\x0A
"