There have been a number of occasions in my recent (no doubt amateurish) 
efforts when I have wished there were (e.g.) a \tl_case_in:NnTF 
statement, in which a token list variable is tested not for equality 
against a single token in each case, but whether it is in a token list 
in each case:

\tl_case_in:Nn <tl-var>
     {
         { token list 1 } {  code 1 }
         { token list 2 } { code 2 }
         ...
     }
     ...
An analogy would be the Select Case statement from dear old 
line-numbered BASIC in which the various alternatives were statements 
like <5,  =6, >7, and so on.

Andrew




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