use strict;
use warnings;
use Benchmark ('cmpthese');

cmpthese(1000000, {
                 double => \&dq,
                 single => \&sq,
                 none   => \&nq
                });

sub dq {
  my $str = "a" x 100;
  my $new_val = "$str";
}

sub sq {
  my $str = "a" x 100;
  my $new_val = '$str';
}

sub nq {
  my $str = "a" x 100;
  my $new_val = $str;
}