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Re: Re^2: Never (qr//)

by diotalevi (Canon)
on May 13, 2003 at 14:44 UTC ( #257764=note: print w/replies, xml ) Need Help??


in reply to Re^2: Never (qr//)
in thread Never-to-use Perl features?

And I recall from looking at the generated optree that =~ /$qr/ and =~ $qr are 100% identical. I don't think anyone here is actually measuring any real difference.

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Re^4: Never (qr//)
by tye (Sage) on May 13, 2003 at 15:52 UTC

    I'd hoped that. I'd heard enough people claiming otherwise that I guessed that perhaps Perl wasn't that smart.

    I also noticed that none of the benchmarking code in this thread was making a straight substitution of /.../o with $qr between the cases. So I picked the code that had the most similar test cases and added one, got results even better than I expected, quadruple checked things because "better than expected benchmarks" almost always means "mistake made".

    Adding another case for /$qr/, I get it being nearly identical to my $_ =~ $qr case (which is faster than /.../o, perhaps just because the qr/.../ part is done outside the scope of the benchmarking; but "fixing" that would be more work than I care to invest at this point).

    So I suspect that diotalevi is correct in both that =~ /$qr/ and =~ $qr produce identical code and that the benchmark results showing qr// to be slower than //o have to do with other code differences between the cases and/or the order that operations get run (or chance).

    Thanks, diotalevi.

                    - tye

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