The tuple file is an ordinary LISP file which is loaded by UNFUG before the actual code production starts. Therefore all LISP language features are available, especially defining additional LISP functions used in the template file may be useful (remember that a function bound to a LISP symbol occurring in angle brackets in a template file is evaluated without arguments, and its string result is inserted into the output file).
One special function, however, is already defined when loading the tuple file,
and this function is used for defining an UNFUG tuple and is simply called
(tuple 'tuple-specification-list). The first symbol of the tuple
specification list is the name of the tuple, then follows a list of variable
names (LISP symbols) which can appear inside UNFUG expressions in
the template file. The remaining lists define the values to be associated with
the variable names on each cycle of the <(UseTuple)> statement.