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@@ -3487,6 +3487,16 @@ in \*(EP.
 You must also supply a text domain.  Use
 .B TEXTDOMAIN
 if you want to use the current domain.
+.SS Boolean Valued Functions
+You can create special Boolean-typed values; see the manual for how
+they work and why they exist.
+.TP
+.BI mkbool( expression\^ )
+Based on the boolean value of
+.I expression
+return either a true value or a false value.
+True values have numeric value one.
+False values have numeric value zero.
 .SH USER-DEFINED FUNCTIONS
 Functions in \*(AK are defined as follows:
 .PP