an interesting question for a bit of golf

Change:

next unless/(?=.*a)(?=.*b)(?=.*c)(?=.*d)(?=.*e)(?=.*f)/i;push@_,$_
[download]

To:

/a/i&/b/i&/c/i&/d/i&/e/i&/f/i&&push@_,$_
[download]

And you can save one character by using a bareword filehandle.