use strict;
my $str = '65.54.188.59 - - [13/Jul/2005:04:10:13 +0200] "GET /fusel/Suchmaschinen.html HTTP/1.0" 404 302 "-" "msnbot/1.0 (+http://search.msn.com/msnbot.htm)"';
my $regex = qr/\G\s*+((\((?:\s*+(?2)\s*+(?(?!\)),)|\s*+[^()',\s]++\s*+(?(?!\)),)|\s*+'[^'\r\n]*+'\s*+(?(?!\)),))++\))|[^()',\s]++|'[^'\r\n]*+')\s*+(?:,|$)/p;
my $subst = '\\n';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html