yeah, in the same sense that D is a breaking change for C, or wayland for X11. the point is that as far as i know it was never intended that existing perl 5 code would be rewritten. unlike the python 2 to 3 change where the intention was that people would convert using 2to3 and later using compatibility modules that allowed writing code that works with both. python 2 development stopped after 12 years, much later than they expected.