use FindBin;
use File::Spec;
use Fcntl qw( O_RDONLY O_EXCL );
my $filename = File::Spec->catfile( $FindBin::Bin, '..', 'html', 'Holzfäller.htm' );

sysopen( my $HTML_FILE, $filename, O_RDONLY | O_EXCL )
    or die "Error: couldn't open file '$filename': $!\n";
... mach was mit $HTML_FILE