So how do I override those methods? I tried calling $self->SUPER::test_via_harness( @_ ) and the object I've received isn't ISA ExtUtils anything.

Writing Makefile for Data::Postponed
Can't locate object method "test_via_harness" via package "main" at Ma
+kefile.PL line 25.
# Looks like your test died before it could output anything.

sub MY::test_via_harness {
    my $self = shift;

    local $_ = $self->SUPER::test_via_harness( @_ );
    s/PERL_DL_NONLAZY=1//g;
    return $_;
}
[download]

Try this:

use ExtUtils::MakeMaker;
package MY;
sub test_via_harness {
  my($self, $perl, $tests) = @_;
  local $_ = $self->SUPER::test_via_harness($perl, $tests);
  s/PERL_DL_NONLAZY=1//g;
  return $_;
}

sub test_via_script {
  my($self, $perl, $tests) = @_;
  local $_ = $self->SUPER::test_via_script($perl, $tests);
  s/PERL_DL_NONLAZY=1//g;
  return $_;
}

package main;
# rest of your Makefile.PL
[download]

the lowliest monk

I chatted with people about this. Apparently $self is blessed into PACK001 which is not ISA anything useful. The proper thing to do is call directly into the MM class (not ExtUtils::MM though). The following code is what actually works. I'm getting a taste of why ExtUtils::MakeMaker is being killed. Yuck. I hope it dies a quick death.

sub MY::test_via_harness {
    local $_ = shift()->MM::test_via_harness( @_ );
    s/\bPERL_DL_NONLAZY=1 +//g;
    return $_;
}

sub MY::test_via_script {
    local $_ = shift()->MM::test_via_script( @_ );
    s/\bPERL_DL_NON_LAZY=1 +//g;
    return $_;
}
[download]