use strict;
use warnings;
use Benchmark;

my @strings = qw(exception:tex exception:mex asdf);

Benchmark::cmpthese( -5, {
    'one' => sub { my @filtered = grep { /exception:(?!tex)/} @strings; },
    'two' => sub { my @filtered = grep { /exception/ && !/tex/ } @strings; },
});
__END__
        Rate  one  two
one 175458/s   -- -15%
two 207611/s  18%   --