This isn't such a silly question as it sounds, since the word "perpetual" crops up frequently in intellectual property licences. One recently-litigated example of this is BMS Computer Solutions Ltd v AB Agri Ltd  EWHC 464 (Ch), a ruling of Mr Justice Sales in the Chancery Division, England and Wales, on Wednesday of last week.
In 1994 BMS, a computer software business, licensed its MillMaster animal feed software to Bibby. Under the termination provisions, the licence would expire after 10 years unless it was terminated earlier; it would also terminate if a parallel technical support agreement between the same parties was not kept up.
* Agri's licence had been terminated. It was true that the word "perpetual" had different shades of meaning, including "incapable of being brought to an end" and "of indefinite duration, but subject to any contractual provisions governing termination". In this case, the second of those interpretations was correct. This being so, there was therefore no incompatibility between the variation agreement and the requirement to keep the support agreement in place, so that requirement continued to have effect. Accordingly, when Agri terminated the support agreement, it also terminated the licence.* The variation agreement was plainly not intended wholly to displace the licence agreement: it stated that the licence would be extended rather than replaced. That indicated that the licence referred to in the variation agreement was subject to the same termination provisions as in the licence agreement.* The very fact that the variation agreement did not refer to the termination provisions in the licence and support agreements indicated that those provisions were intended to continue in force.* The termination provisions were of fundamental importance. If the parties had intended to delete them, they would have done so explicitly rather than just leaving it to be inferred from the use of "perpetual", a term of uncertain meaning. In any event, there was a clear commercial need for the termination provisions to continue to operate. If they did not, there would be no mechanism to bring potentially onerous obligations under the agreement to end.* Use of the software to produce feed above the maximum tonnage was clearly contemplated as being authorised under the variation agreement, since additional payments were provided for. The maximum tonnage figure did not therefore limit the extent of the licence when Agri's business grew. However, it would not be commercially realistic to suppose that the parties intended that there should be no protection for BMS if Agri expanded its activities. It was possible and necessary to interpret the variation agreement by giving it its ordinary and natural meaning so as to require new licence and support agreements to be negotiated for all non-organic tonnage growth.