nl_tokens: FIXME : handler for plugin management
pl_tokens: function ( context ) { return function ( plugin ) { var pattern = context . pattern ; if ( plugin . match ( pattern , opts ) === <mask> ) { plugin . transform ( pattern , opts , function ( items ) { if ( items instanceof Error ) { throw items ; } else { // store transformed pattern in context context . pattern = items ; } } ) ; } else { // plugin doesn't apply } } ; }