$ perl
sub check_context {
    # True
    if ( wantarray ) {
        print "List context\n";
    }
    # False, but defined
    elsif ( defined wantarray ) {
        print "Scalar context\n";
    }
    # False and undefined
    else {
        print "Void context\n";
    }
}

my @x       = check_context();  # prints 'List context'
my %x       = check_context();  # prints 'List context'
my ($x, $y) = check_context();  # prints 'List context'

my $x       = check_context();  # prints 'Scalar context'

check_context();                # prints 'Void context'
__END__
List context
List context
List context
Scalar context
Void context