Generate output on change of value or at end of stream

It is a common problem to have to read an input stream and generate a line of output if one of the columns changes value or when the end of the stream is reached. This generally requires two identical output statements which have to be wrapped in a subroutine to create a DRY solution

I wonder if this problem has a name, if any work has been done on it, and if an approach has been identified that allows this to be coded neatly