It is a domain-specific programming language: it has no features unrelated to fuzzy logic, so it is impossible to even print "Hello, world!".
FCL is not an entirely complete fuzzy language, for instance, it does not support "hedges", which are adverbs that modify the set.
For instance, the programmer cannot write: RULE 0: If (Temperature is VERY COLD) then (Output is VERY HIGH) However, the programmer can simply define new sets for "very cold" and "very high".
FCL also lacks support for higher-order fuzzy sets, subsets, and so on.
None of these features are essential to fuzzy control, although they may be nice to have.