> Always when I run my tests I get:

probably something related with tests path? Is $pack a full path or a relative one? Is a temp dir?

Depending on the OS there are method to see who is maintaining the file open. I suppose you are on linux.. If not inspect also $^E to see last system error.

Your open is better written (as already pointed) in the 3 form; this as the avantage to have the path at disposition when printing errors.

You can also try to see if fileno returns something. Avoid also unnecessary parentheses

my $full_path = '/path/to/file';

#open my $fh, '>', $full_path or die "Unable to open [$full_path] to w
+rite!";
# see tinita below..

open my $fh, '>', $full_path or die "Unable to open [$full_path] to wr
+ite! $!";

...

# this one or some variation..
close $fh or warning "unable to close [$full_path] $! fileno: ".(filen
+o $fh)." -e ".(-e $full_path);

# more checks on directory? 

die if fileno $fh;
[download]

PS you have a typo in the title: correct it for future seekers

L*