in reply to Why does a Perl 5.6 regex run a lot slower on Perl 5.8?

I must be overlooking something, but why wouldn't this code work to remove all instances of "whatever"... 
open (FILE, "a.txt");
$/=undef;
$txt = <FILE>;
$txt =~ s/whatever//sig;

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-- All code is 100% tested and functional unless otherwise noted.

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Re^2: The Deceiver
by diotalevi (Canon) on Aug 13, 2004 at 15:20 UTC
    Finding the things around 'whatever' is different than just removing 'whatever'.
[reply]
      My code was just a literal translation of the OP's remark...
      "As you can see, this code slurps a file and removes all occurences of a certain word (`whatever')."

      -- All code is 100% tested and functional unless otherwise noted.
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      Take a look at how that extract() routine is used a little more closely...
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Re^2: The Deceiver
by perldeveloper (Scribe) on Aug 13, 2004 at 19:35 UTC
    I was trying to make a point about the fact that this code runs incredibly slower on the prepackaged RH9 Perl 5.8.0 compared to the prepackaged (Mandrake 8 I believe) Perl 5.6.1. The example above was whipped up especially for this experiment, after a period of tracking down the exact pieces of code which were slowing down my original Perl programs.

    Only after noticing that the =~ /(.*?) constructs were leading to neverending pauses in the Perl 5.8.0 code, did I realize that adding a ^ anchor would eliminate the inherent ambiguity (the /s switch was on). That's how I made this short example, in which I added the extract subroutine so I can get clear results in the DProf debugger and can make direct comparisons against the Perl versions. I was astounded to see that the slow ratio was not within 1.0 and 2.0 (meaning a tad slower), but somewhere between 500.0 and 1,000.0, explaining why buying new hardware was definitely more expensive than having somebody replace all /(.*?) regexps to /^(.*?) :).
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