#!perl 
use strict;
use Benchmark;

sub normal {
    return 0 unless $_[0];
    @_ = ($_[0] - 1);
    return normal(@_);
}

sub tail {
    return 0 unless $_[0];
    @_ = ($_[0] - 1);
    goto &tail;
}

timethese( 10, {
        "normal" => sub { normal(500000) },
        "tail"   => sub {   tail(500000) },
    }
);

##</code><code>##

    normal: 25 wallclock secs (23.19 usr +  0.59 sys = 23.78 CPU) @  0.42/s (n=10)
      tail: 18 wallclock secs (17.44 usr +  0.03 sys = 17.47 CPU) @  0.57/s (n=10

##</code><code>##

#!perl 
use strict;
use Benchmark;

sub normal {
    return 0 unless $_[0];
    @_ = ($_[0] - 1);
    return normal(@_);
}

sub tail {
    return 0 unless $_[0];
    @_ = ($_[0] - 1);
    goto &tail;
}

timethese( 1, {
        "normal" => sub { normal(1000000) },
        "tail"   => sub {   tail(1000000) },
    }
);

##</code><code>##

Benchmark: timing 1 iterations of normal, tail...
    normal: 123 wallclock secs ( 6.58 usr +  1.13 sys =  7.71 CPU) @  0.13/s (n=1)
            (warning: too few iterations for a reliable count)
      tail:  3 wallclock secs ( 3.50 usr +  0.01 sys =  3.51 CPU) @  0.28/s (n=1)
            (warning: too few iterations for a reliable count)