Python: import string def foo(): s = string.ascii_uppercase return "-".join([''.join(x) for x in zip(*[list(s[z::5]) for z in range(5)])]) 20.41 us

Python: import string def foo(): s = string.ascii_uppercase return "-".join([''.join(x) for x in zip(*[list(s[z::5]) for z in range(5)])]) 20.41 usec, btw. Also how the heck, did it took 7 seconds for a script to do this? ( See slowest solution )