my ($key, $val) = 'MYKEY=MYVAL=2' =~ /^([^=]*)=(.*)/s;
my ($key, $val) = split m{=(?=.*=)}, q{MYKEY=MYVAL=2};

##</code><code>##

use strict;
use warnings;

use Benchmark q{cmpthese};

my $rsMatch = sub
   {
       my ($key, $val) = q{MYKEY=MYVAL=2} =~ /^([^=]*)=(.*)/s;
       return [$key, $val];
   };

my $rsSplit = sub
   {
       my ($key, $val) = split m{=(?=.*=)}, q{MYKEY=MYVAL=2};
       return [$key, $val];
   };

cmpthese(-5,
   {
      Match => $rsMatch,
      Split => $rsSplit
   });

##</code><code>##

         Rate Split Match
Split 26064/s    --   -8%
Match 28250/s    8%    --