uncaught exception: error(existence_error(procedure, p/1), top_level/0)

[William Clodius]

I am trying to teach myself prolog starting with the J. R. Fisher tutorial 
https://www.cpp.edu/~jrfisher/www/prolog_tutorial/pt_framer.html. I worked 
through the first few exercises using gprolog with no problems. I exited prolog 
for a break, but now when I restarted it I find myself unable to define 
procedures and am getting an uncaught exception:

gprolog
GNU Prolog 1.4.5 (64 bits)
Compiled Jul 14 2018, 16:25:15 with /usr/bin/clang
By Daniel Diaz
Copyright (C) 1999-2018 Daniel Diaz
| ?- p(a).
uncaught exception: error(existence_error(procedure,p/1),top_level/0)

I suspect I exited prolog improperly and there is an invalid state somewhere in 
a cache. FWIW I am running on a MacBook with OS X Big Sur version 11.3. Are 
there any suggestions about how to fix this?

smime.p7s
Description: S/MIME cryptographic signature