expect.pl

sub expect (&@) {
  my ($effector, $comparator, $state) = @_;
  my ($before, undef, $after) = map { $_->() } ($state, $effector, $state);
  cmp_ok $before, $comparator, $after;
}

sub make_changes (&) {
  my ($actual) = @_;
  ("!=", $actual);
}

sub make_no_changes (&) {
  my ($actual) = @_;
  ("==", $actual);
}

use Test::More;

my $state = 0;
expect { $state = 1 } make_changes { $state };

done_testing;