That's a fair enough comment: any order was specified in the problem spec. I added to @tests:

my @tests = (
    [[2,7,11,15], 9, [0,1]],
    [[2,7,11,15], 9, [1,0]],
    [[3,2,4], 6, [1,2]],
    [[3,2,4], 6, [2,1]],
    [[3,3], 6, [0,1]],
    [[3,3], 6, [1,0]],
);
[download]

Modified is_deeply:

for my $test (@tests) {
    is_deeply
        sort_arrayref(two_sum($test->[INPUT], $test->[TARGET])),
        sort_arrayref($test->[EXPECTED]);
}
[download]

Appended a new subroutine:

sub sort_arrayref {
    my ($aref) = @_;

    return [ sort { $a <=> $b } @$aref ];
}
[download]

Output now:

1..6
ok 1
ok 2
ok 3
ok 4
ok 5
ok 6
[download]

not sure why you are duplicating the tests ... (?)

one sort_arrayref(two_sum(...)) is enough if you only keep tests with already sorted expectations.

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

I'm not following your prosaic description here. Please post whatever parts of the code you'd write differently.

— Ken