Right! thank you for the pointers/clarification - makes sense now!!!! and this is now valid: (?) 
#!/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;
    }
}
);

[download]
because I get the following now: 
Benchmark: timing 1000000 iterations of double_grep, grep_and, lookahe
+ad_grep...
double_grep: 11 wallclock secs ( 9.06 usr +  0.00 sys =  9.06 CPU) @ 1
+10350.92/s (n=1000000)
  grep_and:  8 wallclock secs ( 8.70 usr +  0.00 sys =  8.70 CPU) @ 11
+4902.91/s (n=1000000)
lookahead_grep: 21 wallclock secs (20.31 usr +  0.00 sys = 20.31 CPU) 
+@ 49231.98/s (n=1000000)

[download]

In reply to Re^6: grep for lines containg two variables by l3v3l
in thread grep for lines containg two variables by smoss74

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.