$str = "   some text    ";
$str =~ s/^\s+//;
$str =~ s/\s+$//;

$str = "   some text    ";
$str =~ s/^\s+|\s+$//g;

#!/usr/bin/perl

use warnings;
use strict;

use Benchmark qw(cmpthese timethese);

sub double_star {
  my $string = shift;
  $string =~ s/^\s*//;
  $string =~ s/\s*$//;
  return $string;
}

sub double_plus {
  my $string = shift;
  $string =~ s/^\s+//;
  $string =~ s/\s+$//;
  return $string;
}

sub single_or {
  my $string = shift;
  $string =~ s/^\s+|\s+$//g;
  return $string;
}

sub replace {
  my $string = shift;
  $string =~ s/^\s*(\S*(?:\s+\S+)*)\s*$/$1/;
  return $string;
}

sub for_star {
  my $string = shift;
  for ($string) { s/^\s+//; s/\s+$//; }
  return $string;
}

sub for_plus {
  my $string = shift;
  for ($string) { s/^\s*//; s/\s*$//; }
  return $string;
}

sub regex_or {
  my $string = shift;
  $string =~ s/(?:^ +)||(?: +$)//g;
  return $string;
}

cmpthese(
  -1,
  {
    'single_or'   => q|single_or(  '    Mary had a little lamb.   ');|,
    'double_star' => q|double_star('    Mary had a little lamb.   ');|,
    'double_plus' => q|double_plus('    Mary had a little lamb.   ');|,
    'replace'     => q|replace(    '    Mary had a little lamb.   ');|,
    'for_star'    => q|for_star(   '    Mary had a little lamb.   ');|,
    'for_plus'    => q|for_plus(   '    Mary had a little lamb.   ');|,
    'regex_or'    => q|regex_or(   '    Mary had a little lamb.   ');|,
  }
);