5/4     In perl, how do you know if an argument given is a scalar, hash,
        or array?
        \_ generally, the use to which it's being put.  And the behaviour
           you see if you use it as a scalar.  Maybe use strict or -wT
           might give you some helpful messages.  -beginning/intermediate
                                                   perl user
        \_ TYPES ARE FOR THE WEAK!
           \_ or for coders who don't know what they are coding
        \_ More to the point is why do you think you'd need to know in perl?
           \_ say you want to overload a method so it takes different
              arguments for backward compatibility. CGI.pm does that.
           \_ Don't know enough about perl to know, but perhaps for things
              like polymorphic function arguments? Perl is pretty ambigious
              about stuff like this... which is why I avoid using it for
              "real" code in projects.
        \_ in some cases you might be able to use ref($var) to find out
           what "type" of variable was passed: some of the return values
           are SCALAR, ARRAY, HASH and REF. (man perlfunc and search for
           ref).