use strict;
use warnings;
my @x = (0..$ARGV[0]||1000);
my $f = $ARGV[1] || 500;
use Benchmark;
use List::Util qw(first);
Benchmark::timethese(-1, {
        Grep => sub{my $y  = grep {$_ == $f} @x},
        Util => sub {my $y = first {$_ == $f} @x}
    }
);