How to Pass MULTIPLE filenames to a Context Menu Shell Command?

Passing a single filename to a context menu shell command is simple:

[HKEY_CLASSES_ROOT\*\shell\MyProgram\Command]
@="program.exe %1"

But if I select multiple files, program.exe is invoked for each such selected file.

What I would like to do instead is invokeprogram.exe only once, passing to it all the filenames currently selected.

How to do this?

You may want to look at this post, as it says that this isn't really possible to pass multiple files to a single instance and you must rely on some form of IPC(Inter process Communication).