Many puddings and yogurtscome in a plastic cup with a tin foil cover glued on. Are you allowedto peel off the cover on Shabbos, or is it a Melacha of Korei'a,tearing? The Orchos Shabbos (12:11) says that if you do not want tokeep the cover for further use then it is permissible to remove thecover either by peeling the lid from the glue or by tearing the coveritself (provided you do not tear any letters).
If you would liketo keep the cover to continue to cover the cup for later use then it ismore problematic. There are two reasons however that make this morelenient. Firstly, the cover is soft and the cup is hard. Tearing softfrom hard is permissible according to some opinions. The question isif a plastic cup is considered hard or soft. The second reason to beMeikil is that the cover is not meant to be permanent and thereforeaccording to the Rema it is not considered Korei'a.
Important Note: We try to convey theTshuva to the best of our ability. We admit that our understanding maynot be accurate. Please also understand that this Tshuva may not be thefinal word on this topic. One should consult a Rav before drawing anyconclusions.