case string [in] patList body patList body ...
      Match string against each of the patList arguments in 
      order.  If one matches, then evaluate the following 
      body argument by passing it recursively to the Tcl 
      interpreter, and return the result of that evaluation. 
      Each patList argument consists of a single pattern or 
      list of patterns.  Each pattern may contain any of the 
      wild-cards described under string match.  If a patList 
      argument is default, the corresponding body will be 
      evaluated if no patList matches string. If no patList 
      argument matches string and no default is given, then 
      the case command returns an empty string.  For example, 

      case abc in {a b} {format 1} default {format 2} a* {format 3}

      will return 3,      

      case a in {a b} {format 1} default {format 2} a* {format 3}

      will return 1, and     

      case xyz {a b} {format 1} default {format 2} a* {format 3}

      will return 2.