\ExplSyntaxOn

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% Compatibility with external packages
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\cs_if_free:NT \str_case_e:nnF
  {
    % \str_case_x was renamed \str_case_e mid-2018. \str_case_x will be removed
    % at the end of 2019:
    %
    %   https://github.com/latex3/latex3/blob/8fcb571ddda61c01773d9746d32cecdbe63afb26/l3kernel/l3obsolete.txt#L65
    \cs_new_eq:NN \str_case_e:nnF \str_case_x:nnF
  }