Perfects of the type I have my dinner eaten are a well-known feature of Irish English dialects. They can be linked to a functionally similar construction in Irish, of the type tá mo dhinneár ite agam (literally “is my dinner eaten at-me”), but also to earlier constructions in Standard English. The issue has sometimes been treated as a competition between two seemingly mutually exclusive explanations, a “substrate” and a “retentionist” hypothesis. This dichotomy can be overcome on the basis of a model of “contact-induced grammaticalisation” (Heine/Kuteva 2005): an existing source structure in the receiving language (English) expands along normal paths, but under a triggering effect of a contact language (Irish), ultimately leading to an apparent duplication of a foreign model. Empirical data comes from historical 18th/19th century corpus material. It provides evidence about the chronology and sociolinguistic setting in which the relevant changes took place. It supports a scenario where both Irish-English bilingualism and exposure to the English source constructions played crucial roles.