Are you sure it wasn't the Meta Object Protocol (MOP) rather than Moose? "A MOP for Perl" inspired endless debate but never amounted to much. In the end I think the Perl 5 community felt it was best left to Perl 6 but I could be wrong as this was all about 20 years ago.
I don't know, this is "second-hand intel" for me, pretty sure I read it in a very old article from someone of the likes of Carl Mäsak, Moritz Lenz or another early-day Rakudo contributor...