As a workaround for #135, I tried to avoid the use of stdout by replacing %DESTEXT%:- with %DEST%, but this didn't work because WebOne deletes the converted output file as soon as the conversion is done, before trying to read it.

On Linux, the simplest fix would be to open the file, then delete it, then return the opened stream (and the OS will properly delete it when the stream is closed). This probably won't for Windows, though.