if the function return or component value is
a non-empty string, and false for an empty string.
.PP
if the function return or component value is
a non-empty string, and false for an empty string.
.PP
than one `%?' control escape in a conditional block.
The `%|' control escape
is also optional, but may be included at most once.
than one `%?' control escape in a conditional block.
The `%|' control escape
is also optional, but may be included at most once.