If your executable would normally be called foo.exe, then instead name it fooX.exe and create a foo.cmd as above (except substitute fooX.exe for yourappX.exe). Distribute both and install them in the same directory.

When the user types foo, foo.cmd will run; it sets the path to null before running fooX.exe.

You may have to tweak the strategy by setting the path commensurate with whatever is required by PerlApp. I've never used that so I cannot advise.

The idea is to prevent the OS searching the path and locatating the wrong copy of the dll. Using a .cmd file is just a simple way of applying the strategy.