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

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] =~ 
/^\[
([^\]]+) # Datum
\]
\s+
\[
([^\]]+) # Fehler
\]
\s+
(?>\[\S+\s([^\]]+)\]\s+)? # falls [client ...] Lookahead 
(.+)
$
/x;
    ) {
        print "matcht 1=>$1< 2=>$2< 3=>$3< 4=>$4< 5=>$5< 6=>$6< 7=>$7<\n";
    }
    else {
        print "matcht nicht\n";
    }
}