Perl Programming/Keywords/wantarray

The wantarray keyword
The function wantarray returns true, if eval or the context of the currently executing subroutine is looking for a list value, and returns false, if the context is looking for a scalar. wantarray returns the undef, if the context is looking for no value (void context).

The result of wantarray is unspecified in the top level of a file, in a wantarray, BEGIN, <tt>CHECK</tt>, <tt>INIT</tt>, <tt>END</tt>, or <tt>UNITCHECK</tt> block. The same is the case for the <tt>DESTROY</tt> method.