PAL

Ptolemaeus Arabus et Latinus

_ (the underscore) is the placeholder for exactly one character.
% (the percent sign) is the placeholder for no, one or more than one character.
%% (two percent signs) is the placeholder for no, one or more than one character, but not for blank space (so that a search ends at word boundaries).

At the beginning and at the end, these placeholders are superfluous.

Abuiafar Hamet filii Joseph, Commentary on the Centiloquium (‘Mundanorum’ version)

Vienna, ÖNB, 2388 · 8r

Facsimile