Whadaheck?
...
The problem was in the

$combined =~ s/[^\x00].*//;
[download]

I tried to print the variable with</code> print "\$combined=",unpack("H*",$combined)," ($combined)\n"; </code> and was really surprised:

¢¼combined=0c0d060a183672756e33 (”Ļ
”č6run3)
$combined=0a183672756e33 (
”č6run3)
Prefix is "model4r"
[download]

(I'd be even more surprised if this went through correctly.)

Guess what was the problem ... well the .* did not match everything. I forgot that without /s dot doesn't match newlines. So the fix is very simple

...
$combined =~ s/[^\x00].*//s;
...
[download]

Actually thinking about this it would probably be better to change the last three lines to:

$combined =~ /^(\x00*)/;
my $prefix = substr($first, 0, length($1));
print qq{Prefix is "$prefix"};
[download]

I should have tested my code better :-(

Jenda
Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.
   -- Rick Osborne

Edit by castaway: Closed small tag in signature