+.PP
+There are three types of variables:
+.I booleans,
+.I text strings,
+and
+.I numbers.
+Boolean values are
+.I true
+if they are "yes", "true", or any non-null integer. Text strings are used 1:1
+without leading and following spaces; there is not way to quote strings. And
+for numbers all decimal integer values are valid.
+.PP
+In addition, some string or numerical variables accept lists of values,
+separated by commas (",").