Microsoft could come up with their own bastardized perl-ish, package it with Windows, or sell it with MSDN stuff.

Actually they did.

The Windows NT 4.0 Resource Kit (a product with a price tag) included a distribution of Perl. I seem to recall it was 5.001 and Microsoft paid Hip Corporation (later to become ActiveState) to port it to Windows. I for one have benefited from that coporate investment in open source software - thank you Microsoft.