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Re: Regular Expression

by Enlil (Parson)
on Feb 09, 2005 at 19:34 UTC ( #429485=note: print w/replies, xml ) Need Help??

in reply to Regular Expression

You can do this a variety of ways, but here are three:
$string =~ m/abc.*xyz|xyz.*abc/i $string =~ m/(?=.*abc)(?=.*xyz)/i; $string =~ /abc/i and $string =~ /xyz/i

The ampersands inside the regular expression will be matched as ampersands and not used as logical operators.


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Re^2: Regular Expression
by nobull (Friar) on Feb 09, 2005 at 20:14 UTC
    $string =~ m/(?=.*abc)(?=.*xyz)/i;

    That unanchored pattern is pathologically inficient. If the string does not match it will try and fail at every character position. Even with a relatively short strings this has a considerable effect.

    use Benchmark; my $string = 'x' x 100; timethese 1_000_000 => { unanchored => sub { $string =~ /(?=.*abc)(?=.*xyz)/i }, anchored => sub { $string =~ /^(?=.*abc)(?=.*xyz)/i }, };

    Benchmark: timing 1000000 iterations of anchored, unanchored...
    anchored: 1 wallclock secs ( 1.30 usr + 0.00 sys = 1.30 CPU) @ 768049.16/s (n=1000000)
    unanchored: 70 wallclock secs (70.12 usr + 0.00 sys = 70.12 CPU) @ 14261.06/s (n=1000000)

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[hippo]: Which people and how long ago?
[hippo]: It's documented in the synopsis of perlsub anyway.

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