Well, and now, something that actually works:
#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
use Path::Tiny;
use File::Temp qw(tempfile);
sub hotpatch {
if ($_[1] eq 'AnyEvent/DNS.pm') {
for my $inc (@INC) {
next if ref $inc;
my $fn = path($inc)->child($_[1]);
if (open my $in, '<', $fn) {
my ($out) = tempfile(UNLINK => 1);
while (<$in>) {
s/sub\s+DOMAIN_PORT\b/sub DOMAIN_PORT () { 1053 }
+sub FORMER_DOMAIN_PORT/;
print {$out} $_;
}
seek($out, 0, 0);
return $out;
}
}
warn "couldn't patch AnyEvent::DNS";
}
return undef;
}
BEGIN { unshift @INC, \&hotpatch }
use AnyEvent::DNS;
BEGIN { @INC = grep not(ref and $_ eq \&hotpatch), @INC }
say AnyEvent::DNS::DOMAIN_PORT();
say AnyEvent::DNS::FORMER_DOMAIN_PORT();