It doesn't for me. The alias seems to be quicker. BUT ...

But the difference is fairly random. If I run the benchmark for a 10000 character long string 20 times, I get very different results. Here are the minimal and maximal rates:

max_alias => 213675
max_ref => 237530
min_alias => 156495
min_ref => 152439

and again when I ran it once more

max_alias => 237530
max_ref => 228833
min_alias => 160000
min_ref => 164204

As you can see, once the maximum and minimum is bigger for one, once for the other. All the speed difference is accidental.

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

print "\n","Length of string: 10000\n";

for (1..20) {
    my $original;
    $original.= chr(int(rand(128))) for 1..1000;
    $original = $original x 10;

    cmpthese (100000,{
        ref =>      sub { my $new = $original; by_ref(\$new)  },
        alias =>    sub { my $new = $original; by_alias($new) },

    });
}

sub by_alias {
   $_[0]  =~ s/\s+//;
}

sub by_ref {
   ${ $_[0] } =~ s/\s+//;
}
[download]

my %data = (min_alias => 999999999, min_ref => 999999999);
while (<>) {
    if (/^(\w+)\s+(\d+)\/s/) {
        my ($typ, $rate) = ($1,$2);
        $data{'min_'.$typ} = $rate if $data{'min_'.$typ} > $rate;
        $data{'max_'.$typ} = $rate if $data{'max_'.$typ} < $rate;
    }
}

print "$_ => $data{$_}\n" for sort keys %data;
[download]

Update: I have perl v5.8.7 running on Windows Vista.