Even though, you can convert MS PowerPoint .ppt directly into .imp (even in batches) using the BulkConvert program that also "ships" with the eBook Publisher software, this perl script (PPT2imp.pl) now allows pre- & post-processing changes to be made using perl scripts!
PPT2IMPA simple batch file called PPT2IMP.bat demonstrates how .IMP ebooks can be created using the workhorse routine 'PPT2imp.pl'. The 'PPT2imp.pl' perl script takes as input a single filename of the PowerPoint .ppt to convert to .imp based on one (rotated) or two 'slides' to a page (not rotated). If the filename contain spaces, then quotes need to surround the parameter!
After executing the sample batch file, the .IMP ebook is produced using temporary files, but the source .html file created gets deleted at the end and is no longer available.
A work-around is to create a .oeb ebook and then 'unpack' it to see that intermediary .html file! However, this doesn't work with the latest eBook Publisher v2.3.8 (that understands .epubs) as this part seems broken; no image files are stored in the resulting .epub).