Well, under Unix you would do this with a named pipe, but I had no idea if named pipes even existed under Windows.

So I ran a google search, and I came up with description of activestate Win32::Pipe module.

Looks to me like it's just what you're looking for.

The way it would work is that you run the perl script, which will open a pipe with the name that is then passed to the DOS program just as if it were a normal file.