use strict;
use warnings;
use Benchmark qw( cmpthese );
use constant
{
    MATCHES =>  6,
    POWER   => 14,
};

my @orig =
(
    qr/.*Error.*/,
    qr/.*error.*/,
    qr/.*ERROR.*/,
    qr/.*FATAL.*/,
    qr/.*Critical.*/,
    qr/.*exception.*/,
);

my @new =
(
    qr/Error/,
    qr/error/,
    qr/ERROR/,
    qr/FATAL/,
    qr/Critical/,
    qr/exception/,
);

my   $total = MATCHES * (2 ** POWER);
my   @lines = <DATA>;
push @lines, @lines  for 1 .. POWER;

cmpthese
(
    10,
    {
        orig => sub { find(\@orig, \@lines) },
        new  => sub { find(\@new,  \@lines) },
    }
);

sub find
{
    my ($res, $lines) = @_;
    my  $count        = 0;

    for my $line (@$lines)
    {
        $line =~ /$_/ && ++$count for @$res;
    }

    $count == $total
        or die "Expected $total, counted $count";
}

__DATA__
Line 1
This contains an Error: 1
Line 3
Line 4
This contains an error: 2
This contains an ERROR: 3
Line 7
FATAL (4)
Line 9
This problem is Critical
Line 11
exception