#!/usr/bin/perl

use strict;
use warnings;
use Benchmark ':all';

my $original = ' Bla Test Jetzt kommen nochmal Leerzeichen         ';
my $string;
my $re1 = qr/^\s+/o;
my $re2 = qr/\s+$/o;

sub one 
 {
  $string = $original;
  $string =~ s/$re1//o;
  $string =~ s/$re2//o;
 }

sub two 
 {
  $string = $original;
  $string =~ s/^\s+//;
  $string =~ s/\s+$//;
 }

cmpthese (200000, { one => sub { &one; }, two => sub { &two; } } );