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

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

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

...

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

# more checks on directory? 

die if fileno $fh;