When a reference to a hash is evaluated in scalar context, as in your if statement, Perl stringifies it into something like HASH(0x80182c2b8), where the hexadecimal number is the memory location where the actual hash is stored. So by checking for /HASH\(/, you can see that it's a hash reference (or a string that looks like one), but that doesn't tell you whether the hash it points to has any keys and values. Your if(! test will only return true if the value for the 'QUESTION_TEXT' key isn't a hash reference at all. Try this to prove it:

$h = {};  # create reference to an empty hash
print $h; # prints HASH(0xSOMETHING)
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It sounds like what's happening in your case is that $hh{QUESTION_TEXT} sometimes holds a hash reference, and sometimes holds a string. You can check for that first with the ref function. That will tell you whether the value is a hash reference, and if it is, then you can dereference it as stevieb and I both showed, to see if it's empty.