No, but you can get the same effect by:
my $pid = open LS, 'ls -l |' or die $!;
my $result = do{ local $/; <LS> };
Of course, once you read the input, $pid will no longer be valid as ls will have terminated. But then, the same would be true for backticks.
All of which leads to the question, why do you want the pid?
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
The "good enough" maybe good enough for the now, and perfection maybe unobtainable, but that should not preclude us from striving for perfection, when time, circumstance or desire allow.