minimal fixup to also accept an array of 1 item

This has been breaking since Perl 5.10, because the single-arg shorthand constructor apparently used to come through as a scalar, and now comes through as an array with one element.
I've added a case that handles an-array-with-one-element as well, so it should behave correctly in older Perl versions as well as new.
Haven't changed anything else (no, no additional tests, for example...  frankly I'm not familiar enough with that constructor shorthand idiom to know how to test it properly)
But since I had some code that depended on this, I figured I'd fix the module rather than rewrite the other code.