Where have I gone astray?

Well, you're forgot that cmd.exe isn't bash, and doesn't like single quotes

See perlrun, Behind the GUI lives the Shell

But the really real problem is you fell for Unix tool-and-filter philosophy. :)

This is how your rename files, Re: Renaming files in a directory in sequence, make a list of renames, then human you review the list for any mistakes, then finally do the rename

Dont assume your program is correct, esp one typed on the commandline