[Add URLs for prolog, background, etc.] "Programming in Logic", a declarative language (sort of) popular in Europe. See Playing Prolog and Playing predicate logic.
SICSTus Prolog has a "complete Tcl interface" [L1 ].
also ECLiPSe (not to be mistaken with the IDE [L2 ]) has an interface to Tcl/Tk [L3 ]. A description and some first steps in are listed at ECLiPSe CLP.
Haven't there been collaborations between Prolog and Tk?