I'm using perl 5.6.1, and I don't get those results. Here's the script I'm using. I was just curious about leading spaces by itself, so I threw that in, but the WHILE_RE version is definitely slower than either the SEXEGER or the SINGLE_RE version. And on the leading & trailing white space stripping, the LEADTRAIL is version is quicker than the LTSAVE version. 
#!/usr/local/bin/perl -w

use strict;
use Benchmark;

my $str = "   a b  c   d    ";

timethese(-5, {
 LEADING=>\&leading,
 LEADTRAIL=>\&lead_trail,
 LTSAVE=>\&lt_save,
 SEXEGER=>\&sexeger,
 SINGLE_RE=>\&single_re,
 WHILE_RE=>\&while_sub,
});

sub leading {
 local $_ = $str;
 s/^\s+//;
 $_;
}

sub lead_trail {
 local $_ = $str;
 s/^\s+|\s+$//g;
 $_;
}

sub lt_save {
 local $_ = $str;
 s/^\s*(.*?)\s*$/$1/;
 $_;
}

sub sexeger {
 local $_ = reverse $str;
 s/^\s+//;
 reverse $str;
}

sub single_re {
 local $_ = $str;
 s/\s+$//;
 $_;
} 

sub while_sub {
 local $_ = $str;
 1 while s/\s$//;
 $_;
} 

~/tst >./tst3
Benchmark: running LEADING, LEADTRAIL, LTSAVE, SEXEGER, SINGLE_RE, WHI
+LE_RE, eac
h for at least 5 CPU seconds...
   LEADING:  5 wallclock secs ( 5.00 usr +  0.00 sys =  5.00 CPU) @ 77
+596.80/s (
n=387984)
 LEADTRAIL:  5 wallclock secs ( 5.22 usr +  0.00 sys =  5.22 CPU) @ 26
+504.21/s (
n=138352)
    LTSAVE:  5 wallclock secs ( 5.18 usr +  0.00 sys =  5.18 CPU) @ 18
+690.54/s (
n=96817)
   SEXEGER:  4 wallclock secs ( 5.35 usr +  0.00 sys =  5.35 CPU) @ 57
+972.52/s (
n=310153)
 SINGLE_RE:  5 wallclock secs ( 5.23 usr +  0.00 sys =  5.23 CPU) @ 56
+434.42/s (
n=295152)
  WHILE_RE:  6 wallclock secs ( 5.00 usr +  0.00 sys =  5.00 CPU) @ 36
+090.00/s (
n=180450)

[download]
Update: I cut 'n pasted the code and output, then fixed LTSAVE, then forgot to repaste. I guess no one looked closely enough to notice that LT_SAVE was actually beating LEADTRAIL. Its all fixed now though :)

In reply to Re: japhy blabs about regexes (again) by runrig
in thread japhy blabs about regexes (again) by japhy

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