case & string

Hi! I try use CASE and string variable and a have error.... I checked User's guide 2.0 <https://bird.network.cz/?get_doc&f=bird.html&v=20>.... CASE use operator ~.  This operator applies to string variables. What am I doing wrong? [root@wine etc]# cat 123.conf && bird -c ./123.conf -p function teststring(string myvar) -> bool   {   case myvar {     "text A" : print "A"; return true;     "text B" : print "B"; return true;     "text C" : print "C"; return true;     else : print "unknown"; return false;     }   } bird: ./123.conf:4:12 syntax error, unexpected TEXT -- Regards, Mikhail Mayorov