Karl grew up travelling around Canada, the United States, and Europe as an "army brat". His family later settled in Kingston, Ontario. After high school Karl did some additional travelling, and upon returning to Canada he briefly attended Carleton University and was a member of their drama society. In 1977 he joined the National Arts Centre's English theatre company. Karl has appeared in numerous Canadian stage productions as well as performing in film and television. He has starred in the series E.N.G. and Total Recall 2070, as well as the 2002 mini-series Trudeau, where he portrayed Canadian Prime Minister, John Turner. Karl is married to Sharon Jackson-Pruner and they have two children.