Titel Text (A12-3)
3-123.7 Just another text 3-123.8 Some more text
A12.34 Another item B56.78 Yet another item
Another Titel Text (B23-9)
1-22a.b Just another text 
2-3cd.e Some more text
W12.34 Another item 
Z56.78 Yet another item

##</code><code>##

Titel Text (A12-3);3-123.7 Just another text
Titel Text (A12-3);3-123.8 Some more text
Titel Text (A12-3);A12.34 Another item
Titel Text (A12-3);B56.78 Yet another item

##</code><code>##


use strict;
use warnings;

my $outcome;
my $previous;

while(<DATA>)	{
		$outcome = "";
		chomp;
				
		$_=~ s/\s(\d\-\d\w{2}(\.\w+)?)/\n$1/g;
		$_=~ s/\s([A-Z]\d{2}(\.\d+)?)/\n$1/g;
		
				
			
		if (/\s?\d\-\d\w{2}(\.\w+)?.+|\s?[A-Z]\d{2}(\.\d+)?.+|\(\w+\-\d+\)$/)
		
			{
				
				
				if (/\(\w+\-\d+\)$/ )	{ 					
					
					$previous = $_;
					}
					else	{
					
					
					$outcome = "$previous;$_";
					}
            $outcome=~s/^\s+$//g;								
			
			print  "$outcome\n";
			}		
			
}

__DATA__
Titel Text (A12-3)
3-123.7 Just another text 3-123.8 Some more text
A12.34 Another item B56.78 Yet another item
Another Titel Text (B23-9)
1-22a.b Just another text 
2-3cd.e Some more text
W12.34 Another item 
Z56.78 Yet another item
Some trash
Some trash