... noting that the "//" operator is, IIRC, a relatively recent addition to the language. You should have it, but you (or some backwater web-hosting companies who need not be named ...) conceivably might not. See perldoc perlop on your system; look for the heading “C-style Logical Defined-Or.”
And that's right where I am (CENTOS 6 packaged Perl).
I know and heartily approve the "//" operator (except when I somehow get confused and use backslashes), but don't want to have to write special code each time I print something that I can't prove is defined quickly. However, the Dumper suggestion (and related) is useful, I'm just embarrassed I didn't think of it myself (that's for complex structures! In debugging!).