$n =  scalar( split ',', $str );
print "$n\n";

##</code><code>##

use strict;
use Benchmark qw/timethese cmpthese/;

my $str = join ',',map{('a'..'z')[rand 26] x (1 + rand 5)}0..1000;

cmpthese( timethese(10000, {
        'split_anonymous' => '&split_anonymous',
        'split_simple' => '&split_simple',
    }) );

sub split_anonymous
{
    my $n = @{[split ',', $str]};
    #print "$n\n";
}

sub split_simple
{
    my $n = scalar split ',', $str;
    #print "$n\n";
}

##</code><code>##

Benchmark: timing 10000 iterations of split_anonymous, split_simple...

split_anonymous: 19 wallclock secs (19.05 CPU) @ 525.02/s (n=10000)
split_simple: 16 wallclock secs (15.77 CPU) @ 634.32/s (n=10000)

                 Rate split_anonymous    split_simple
split_anonymous 525/s              --            -17%
split_simple    634/s             21%              --