You simply have a hash where each element in the set represents a key and its corresponding value is 1 or some other true value.

   my (%fruits,%vegetables);
   $fruit{apple}=1;
   $fruit{orange}=1;
   $fruit{banana}=1;
   $vegetable{corn}=1;
   $vegetable{carrot}=1;
   
   #test whether apple is in the set fruit
   if($fruit{apple}){  #test for inclusion in a set
      print "apple is a fruit";
   }
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