How to test only for the language-code but not for the country?

[Friedli Beat [UFA AG Her]]

Title: How to test only for the language-code but not for the country?

I want to test the Accept-Language and show a french message if the user speaks french.

But the following code doesn't take care of the Accept-Language fr-ch.

<logic:equal value="fr" header="Accept-Language">
  Welcome french
</logic:equal>

And this code doesn't take care of the Accept-Language fr-ch.

<logic:equal value="fr-ch" header="Accept-Language">
  Welcome french
</logic:equal>

Do I have to write my own tag? Has anybody allready an apropriate tag?

thanks

Beat Friedli