You're right. A plain filehandle (as likely opened by File::Binary) is an IO::Handle object. And these don't know about the ->binmode method:

Q:\>perl -le "open my $fh, $^X or die $!; $fh->binmode"
Can't locate object method "binmode" via package "IO::Handle" at -e li
+ne 1.
[download]

So the easiest fix approach would be to use File::HandleIO::File objects instead of filenames, but I haven't looked at what API File::Binary uses. It could also make sense to patch File::Binary to use files (as the module name implies).

So the easiest fix approach would be to use File::Handle objects instead of filenames

uh? It works when you pass a file name. It creates an IO::File object, and they do have binmode.

And did you mean FileHandle? It's been renamed to IO::File. Use the latter instead.