#!/usr/bin/perl -w
# usage : ./this_script.pl input_file > captured_benchmarks
use strict;
use Benchmark;
my @data = do {
   open(my $fh, '<', $0) or die;
   <$fh>
};
timethese (1000000,
    { grep_and => sub{
    my @res1 = grep /GGGGGACACCTTCTCTCTCT/ && /RH_MEa0001bG06/,@data;
    },
    double_grep => sub{
    my @res2 = grep /GGGGGACACCTTCTCTCTCT/,grep /RH_MEa0001bG06/,@data;
    },
    lookahead_grep => sub{
    my @res3 = grep /^(?=.*GGGGGACACCTTCTCTCTCT)(?=.*RH_MEa0001bG06)/,@data;
    }
}
);

##</code><code>##

Benchmark: timing 1000000 iterations of double_grep, grep_and, lookahead_grep...
double_grep: 11 wallclock secs ( 9.06 usr +  0.00 sys =  9.06 CPU) @ 110350.92/s (n=1000000)
  grep_and:  8 wallclock secs ( 8.70 usr +  0.00 sys =  8.70 CPU) @ 114902.91/s (n=1000000)
lookahead_grep: 21 wallclock secs (20.31 usr +  0.00 sys = 20.31 CPU) @ 49231.98/s (n=1000000)