my $tmp;
$entry =~ s/(\[email\]|\[email=(.*)\])(.*)\[\/email\](?!\[\/email\])(?{ if(!defined($2) or $2 eq '') {$tmp = $3 }else{ $tmp = $2 } })/<a href=\"mailto:$tmp\">$3<\/a>/ig;
print "Ich bin 1 $1<br>";
print "Ich bin 2 $2<br>";
print "Ich bin 3 $3<br>";
print $tmp;