my $x = \" VERY VERY BIG STRING .....";
  my $len = length( $$x );
##</code><code>##

my $string = 'Long string' x 100000;
sub psau() { print grep { /\b$$\b/ } `ps au` } # POSIX platforms
sub bar    { psau }
sub foo    { my $s = shift; psau }
sub mod    { my $s = shift; $s =~ s/Long/LONG/g; psau }

psau;
bar($string);
foo($string);
mod($string);
psau;

##</code><code>##

use Devel::Size qw< size total_size >;

sub size_print($\$) {
    my ($name, $ref) = @_;
    printf "%20s %5d %5d\n", $name, size($ref),
    total_size($ref);
}

my $string = 'Long string' x 100;
printf "%20s %5s %s\n", qw<Name size total_size>;
size_print '$string', $string;

my $collection = [ ];
size_print '$collection (empty)', $collection;

push @$collection, \$string;
size_print '$collection ( one )', $collection;

push @$collection, \$string;
size_print '$collection ( two )', $collection;

__END__
                Name  size total_size
             $string  1134  1134
 $collection (empty)    24    88
 $collection ( one )    24  1278
 $collection ( two )    24  1302

##</code><code>##

use Benchmark qw<cmpthese>;

my $string      = 'Long string' x 1000;
my $really_long = $string x 100;
my $ref         = \$string;
my $long_ref    = \$really_long;

cmpthese(-5, {
    map { $_ => "length($_)" } qw< $string $$ref $really_long $$long_ref >
});
__END__
                   Rate   $$long_ref        $$ref $really_long      $string
$$long_ref   17305170/s           --          -9%         -36%         -38%
$$ref        18937129/s           9%           --         -30%         -32%
$really_long 27185304/s          57%          44%           --          -2%
$string      27870647/s          61%          47%           3%           --