__DATA__
Some Company; Some Street 52
12345 City1
Another Company; Another Street 63
23456 City2
Yet Another Company; New Street 11
34546 City3

##</code><code>##

use strict;
use warnings;


while(<DATA>)	{
	
	$_=~s/([\w; ]+\d+)\n(\d{5})/$1$2/gms;
	print;
}

##</code><code>##

use strict;
use warnings;


while(<DATA>)	{
$_=~s/(\d{5})/;$1;/g;
	$_=~s/\n//gms;
	$_=~s/(\d{5}; \w+)/$1\n/g;
	
	print;
}