sed and Mac OS X differences with to upper, to lower and whole capture control sequences

Question

I am trying to take the last two letters out of a filename which are uppercase and append them to the filename in lowercase. I expeceted the command:

Answer 1

awk alternative:

ls | awk '{print $0 tolower(substr($0,length($0)-1,2))}'

Answer 2

OSX (BSD) sed doesn't support functions \L, \E etc. Install gnu sed on Mac using this option:

brew install gnu-sed