The first run of the first test will suck <DATA> dry. Every other run of that test and every run of the other tests will never call the function being benchmarked. Try:

my @data = <DATA>;

my $result = timethese($count, {
   i_sep   =>
      sub { my %heap; foreach (@data) { i_sep(  \%heap, $_) } },
   i_peers =>
      sub { my %heap; foreach (@data) { i_peers(\%heap, $_) } },
   i_noop  =>
      sub { my %heap; foreach (@data) { i_noop( \%heap, $_) } },
});
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It's good to check the result of tests by adding debug statememnts that will be removed when the tests are known to work.