use Benchmark;
timethese (1000000, {
        'unpack' => q{  my $foo = "test    ";
                        $foo = unpack("A8",$foo); },
        'regex'  => q{  my $foo = "test    ";
                        $foo =~ s/\s+$//;},
        'xeger'  => q{  my $foo = reverse "test    ";
                        $foo =~ s/^\s+//;
                        $foo = reverse $foo;}
} );
    

##</code><code>##

Benchmark: timing 1000000 iterations of regex, unpack, xeger...
     regex:  6 wallclock secs ( 5.71 usr +  0.00 sys =  5.71 CPU) @ 175131.35/s (n=1000000)
    unpack:  7 wallclock secs ( 5.91 usr +  0.00 sys =  5.91 CPU) @ 169204.74/s (n=1000000)
     xeger:  9 wallclock secs ( 9.26 usr +  0.00 sys =  9.26 CPU) @ 107991.36/s (n=1000000)