#!/usr/bin/perl
use strict;
use warnings;

my $regex = qr{
    /^\[
    \S+\s+
    (\S+)\s+
    ([0-9]+)\s+([0-9:]+)\s+([0-9]+) # Datum
    \]
    \s+
    \[
    ([^\]]+) # Fehler
    \]
    \s+
    (?>\[\S+\s([^\]]+)\]\s+)? # falls [client ...] Lookahead 
    (.+)
    $
}x;

my @test;
push @test,'[Thu Nov 08 22:59:19 2012] [error] Hostname www.......de provided via SNI, but no hostname provided in HTTP request';
push @test,'[Fri Nov 09 09:49:30 2012] [error] [client 8.1.1.1] Can\'t modify constant item in scalar assignment at /script.pl line 16, near "\'schiess mich tot\';", referer: https://.......pl';
for (my $z = 0; $z < scalar @test; $z++) {
    print "Zeile $z: ";
    if (
        $test[$z] =~ $regex
    ) {
        print "matcht 1='$1' 2='$2' 3='$3' 4='$4' 5='$5' 6='$6' 7='$7'\n";
    }
    else {
        print "matcht nicht\n";
    }
}

my $regex = qr{
    ^\[
    \S+\s+
    (\S+)\s+
    ([0-9]+)\s+([0-9:]+)\s+([0-9]+) # Datum
    \]
    \s+
    \[
    ([^\]]+) # Fehler
    \]
    \s+
    (?>\[\S+\s([^\]]+)\]\s+)? # falls [client ...] Lookahead 
    (.+)
    $
}sx;