gistfile1.pl

grammar STRING {
    proto token TOP {*}
    token TOP { '"' ( <ESCAPE> | <-["]> )* '"' }
    token TOP { "'" ( <ESCAPE> | <-[']> )* "'" }    
    token ESCAPE { "\\" <( "\\" | "'" | '"' )> }
  }
  
class STRING {
    method TOP ($/) { make [~] $0.map(-> $/ { $<ESCAPE>.made || $() }) }     
    method ESCAPE ($/) { make $() }
}