He found this gem:
Programming Perl, by Larry Wall and Randal L. Schwartz.
Editor: Tim O'Reilly himself!
".... the hottest new UNIX utility in years .... "
Jan 1991: First edition
August 1991: Minor corrections.
March 1992: Minor corrections.
Line that up with the Perl release history:
Perl 5 hadn't even started yet. :-)
And Perl 6 isn't even done yet, yet gaal's hardcore self ports Cache::Memcached to Perl 6.
And with that,