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;}
} );