use strict;
use warnings;
use Data::Dump qw/pp dd/;

$|=1;


BEGIN {

    $\="\n";
    my $old =  $SIG{__WARN__};
    $SIG{__WARN__} = sub {
        my ( $msg  ) = @_ ;

        if ($msg =~ /Constant subroutine DOMAIN_PORT redefined/ ) {
            $SIG{__WARN__} = $old;
            print "REDEFINED", pp caller;

            package ALIEN;
            no warnings "redefine";
            sub DOMAIN_PORT() {
                666
            }

        }

}



}

sub ALIEN::DOMAIN_PORT() {
    "DUMMY"
}



package ALIEN;


sub DOMAIN_PORT() {
    53
}



BEGIN {
    print "pre compile";
}

sub test {
    print "Inside test: ", DOMAIN_PORT;
}

BEGIN {
    test();
    print DOMAIN_PORT;
}



##</code><code>##

REDEFINED("main", "d:/tmp/pm/patch_constant.pl", 42)
pre compile
Inside test: 53
53