use Benchmark qw(:hireswallclock timethese);
timethese( 1000000,{
  one => sub { require Benchmark },
  two => sub { require Benchmark; require Benchmark },
});
__END__
$ perl 1
Benchmark: timing 1000000 iterations of one, two...
 one: 2.43888 wallclock secs ( 1.70 usr +  0.00 sys =  1.70 CPU) @ 588235.29/s (n=1000000)
 two: 5.11982 wallclock secs ( 2.77 usr +  0.00 sys =  2.77 CPU) @ 361010.83/s (n=1000000)