Means you run an apt update or similar recently which updated to newer versions of some files concerning perl amd mail. Either that or someone hacked your system and put their own copies there :-)
I'll assume it was the former, if so merely run:
on your command line and rkhunter will update to the new binaries for these 3.
NB: you should always run the above if you ever apt-get update something or other on your system, or install something new.