cmpthese( -1, { 'a' => GRT($s), 'b' => ST($s) } ) ;

[download]
This calls both GRT and ST just once, and uses their output as the code to eval and benchmark. That's not what we want. Instead, we need 
cmpthese(-3, {
    grt => sub { GRT($s) },
    st  => sub { ST($s) }
});

[download]

It still seems that ST is much faster: 

      Rate  grt   st
grt 2.75/s   -- -76%
st  11.6/s 320%   --

[download]

But, notice the regex is different when splitting the string: 

       split m{(?<!\A)(?=>>>)}, $s     # GRT
       split       (/^(?=>>> )/m, $s)  # ST

[download]

So, let's add a test to verify the results stay correct 

use Test::More tests => 1;
is GRT($s), ST($s), 'same';

[download]

and we can use the simpler regex from ST in GRT. Fortunately, the test remains successful, and the results are now different: 

1..1
ok 1 - same
      Rate  st grt
st  11.7/s  -- -3%
grt 12.1/s  3%  --

[download]

An insignificant difference, but at least ST doesn't seem to be much faster now.

Benchmarking and optimisation are hard.

map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re^6: schwartzian transform problem by choroba
in thread schwartzian transform problem - Solved by Cristoforo

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