I have this:

\definemode[EN,FR,RU,PT][keep]
\doifmodeelse{EN}
  {
    \disablemode[FR]
    \disablemode[RU]
    \disablemode[PT]
  }
  {
    \doifmodeelse{FR}
    {
      \disablemode[EN]
      \disablemode[RU]
      \disablemode[PT]
    }
    {
      \doifmodeelse{RU}
      {
        \disablemode[EN]
        \disablemode[FR]
        \disablemode[PT]
      }
      {
        \doifmodeelse{PT}
        {
          \disablemode[EN]
          \disablemode[FR]
          \disablemode[RU]
        }
        {
          \enablemode[EN]
        }
      }
    }
  }

But for every language added this becomes more and more complex. I was wondering what would be a good approach to simplify it. 

I want to make sure that one and only one of these modes is active and that if no mode is entered on the command line the mode is EN.

Gerben Wierda (LinkedIn <https://www.linkedin.com/in/gerbenwierda>)
R&A IT Strategy <https://ea.rna.nl/> (main site)
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