The Collaborative International Dictionary of English v.0.48:

Perpetually \Per*pet"u*al*ly\, adv.
   In a perpetual manner; constantly; continually.
   [1913 Webster]

         The Bible and Common Prayer Book in the vulgar tongue,
         being perpetually read in churches, have proved a kind
         of standard for language. --Swift.
   [1913 Webster]

WordNet (r) 3.0 (2006):

perpetually
    adv 1: everlastingly; for all time; "rays...streaming
           perpetually from the sun"- Stuart Chase
    2: without interruption; "the world is constantly changing"
       [syn: constantly, always, forever, perpetually,
       incessantly]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "perpetually":
   abidingly, ad infinitum, always, at all times, ceaselessly,
   changelessly, constantly, continually, continuously, daily,
   daily and hourly, day after day, day and night, endlessly,
   enduringly, eternally, ever, ever and anon, everlastingly,
   every day, every hour, every moment, hour after hour, hourly,
   in perpetuity, incessantly, indestructibly, infinitely, inflexibly,
   interminably, invariably, lastingly, month after month,
   never-endingly, night and day, on and on, perdurably, perennially,
   permanently, rapidly, regularly, right along, rigidly, statically,
   steadfastly, steadily, sustainedly, time without end, unceasingly,
   unchangingly, unendingly, unintermittently, uninterruptedly,
   unvaryingly, unwaveringly, without cease, without end,
   without letup, without stopping, world without end,
   year after year