bench.pl

use strict;
use warnings;

use Benchmark qw/cmpthese timethese/;

my @class = qw/Foo Foo::Bar Foo::Bar::Baz/;

sub substr_c {
    my $class = shift;
    substr $class, 1 + rindex $class, ':';
}

sub split_c {
    my $class = shift;
    (split /::/, $class)[-1];
}

sub regexp_c {
    my $class = shift;
    $class =~ /:([^:]+)$/;
    $1 || $class;
}

cmpthese timethese 1000000 => {
    substr => sub { substr_c($_) for @class },
    split  => sub { split_c($_)  for @class },
    regexp => sub { regexp_c($_) for @class },
};
__END__
Benchmark: timing 1000000 iterations of regexp, split, substr...
    regexp:  3 wallclock secs ( 2.04 usr +  0.00 sys =  2.04 CPU) @ 490196.08/s (n=1000000)
     split:  2 wallclock secs ( 1.86 usr +  0.01 sys =  1.87 CPU) @ 534759.36/s (n=1000000)
    substr:  1 wallclock secs ( 1.04 usr +  0.00 sys =  1.04 CPU) @ 961538.46/s (n=1000000)
           Rate regexp  split substr
regexp 490196/s     --    -8%   -49%
split  534759/s     9%     --   -44%
substr 961538/s    96%    80%     --