You can avoid hitting the disk (even though that's great for debugging) by using an in-memory file in your @INC hook:

                open my $out, \my $buffer
                    or die "Couldn't patch AnyEvent::DNS; your Perl do
+es not support in-memory filehandles";
                while (<$in>) {
                    s/sub\s+DOMAIN_PORT\b/sub DOMAIN_PORT () { 1053 } 
+sub FORMER_DOMAIN_PORT/;
                    $buffer .=  $_;
                }
                return $out;

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In reply to Re^3: How to redefine a modules private function? by Corion
in thread How to redefine a modules private function? by sectokia

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