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.

Theon of Alexandria, 〈Commentum in Almagesti〉 (tr. Giovanni Battista Teofilo)

Urbino, BU, Fondo del Comune – Busta 120 (28) · 205v

Facsimile