use Benchmark qw(cmpthese);
my $tests = -25;
sub single { print 'This is a test'; }
sub double { print "This is a test"; }
cmpthese($tests,{
 single => \&single,
 double => \&double
 });
__OUTPUT__
            Rate single double
single 1952135/s     --   -16%
double 2313034/s    18%     --