ref() returns "REF" for a reference to a reference: 
> perl -e 'print ref \\"test"'
REF

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In general, it's not smart to rely on any specific value for ref() beside true or false, except when you really have to, i.e. for serialization. The value of ref() has changed for some types (regexes (?), filehandles...), and AFAIK there is no guarantee it won't change again.

edit: after reading perlfunc on it, it appears you can count on the return values given there (which do not cover all perl data types):

SCALAR ARRAY HASH CODE REF GLOB LVALUE and the package name for a blessed object (though you shouldn't use that)

"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: ref eq "REF" by Joost
in thread ref == "REF" by gaal

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