sub somefunc {
    my $arg = shift;
    print "doing something with $arg\n";
    return unless defined wantarray;
    print "doing expensive return value calc\n";
    return wantarray ? ('foo','bar') : 'quz';
}
somefunc("a");  # just prints "doing something with a"
my $x = somefunc("b");
print "$x\n";             # prints "quz"
my @y = somefunc("c");
print join(",",@y),"\n";  # prints "foo,bar"