Is there a way to determine whether a variable ($x) is a reference, and if so, what type of thing it refers to?

For example, I want to do something like: 

if ( is_not_a_reference($x) ) {
  print $x;
}
elsif ( is_a_hash_ref($x) ) {
  process_hash( %$x );
}
else {
  . . .
}

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Originally posted as a Categorized Question.

In reply to How do I determine the type of a reference? by Anonymous Monk

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