#!/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, WHILE_RE, eac
h for at least 5 CPU seconds...
   LEADING:  5 wallclock secs ( 5.00 usr +  0.00 sys =  5.00 CPU) @ 77596.80/s (
n=387984)
 LEADTRAIL:  5 wallclock secs ( 5.22 usr +  0.00 sys =  5.22 CPU) @ 26504.21/s (
n=138352)
    LTSAVE:  5 wallclock secs ( 5.18 usr +  0.00 sys =  5.18 CPU) @ 18690.54/s (
n=96817)
   SEXEGER:  4 wallclock secs ( 5.35 usr +  0.00 sys =  5.35 CPU) @ 57972.52/s (
n=310153)
 SINGLE_RE:  5 wallclock secs ( 5.23 usr +  0.00 sys =  5.23 CPU) @ 56434.42/s (
n=295152)
  WHILE_RE:  6 wallclock secs ( 5.00 usr +  0.00 sys =  5.00 CPU) @ 36090.00/s (
n=180450)