nl_tokens: see https : // github . com / joyent / node / blob / v0 . 8 . 8 - release / lib / domain . js#L53
pl_tokens: function emitError ( currentDomain , err ) { /*jshint camelcase: false*/ util . _extend ( err , { domain : currentDomain , domain_thrown : <mask> } ) ; currentDomain . emit ( 'error' , err ) ; currentDomain . exit ( ) ; }