Returns true if the context of the currently executing subroutine or
eval is looking for a list value.  Returns false if the context is
looking for a scalar.  Returns the undefined value if the context is
looking for no value (void context).
wantarray()'s result is unspecified in the top level of a file,
in a BEGIN
, UNITCHECK
, CHECK
, INIT
 or END
 block, or
in a DESTROY
 method.
This function should have been named wantlist() instead.