Interpolation is short for "variable interpolation", and you are correct, variable interpolation is not done on single quoted strings. But there are many cases where meta-characters will need to be escaped for the string you are working with to act as you expect it to act, and this is one of those cases.

So you are correct, the backslash single quote makes the perl interpreter believe you intend for the ending single quote to be part of the string which then ends 2 lines later.

-Scott