if ($sender = "sender A")
{ 
   if ($subject =~ "some text")
     {
       if ($body =~ "some other text")
          {   return "type 1"; }
       elsif ($body =~ "some other other text)
          {return "type 2"; }
       else {return "type 3";}
     }
   elsif ($subject =~ "some other subject")
...