See OP. Most of those who runs linux have outdated version of Python, Ruby and Perl. And they used to use Perl, Ruby and Python software without upgrading all their stuff.
As does every version of MacOS X. Many versions of MacOS come with two Perls, at least one of which is used by many system functions, is known to be outdated, and some of those system functions depend on the bugs of the outdated version, which is why you shouldn't muck with it.
All of that is why it's recommended that you install your own Perl (or even multiple versions of your own Perl) so that a) you don't bork the system Perl by updating some module or other, and b) don't have your programs borked when the system decides to overwrite versions that you're depending on when you do a system version upgrade. The same applies for Ruby and Python. I work mostly in Perl and Ruby, and I have my own installs of both on my dev machines and on the production servers.
So recommending an upgrade that fixes a some bugs or adds some features shouldn't be that big of a deal. And I find that Perl is much more robust during upgrades than Ruby-- I can usually move to a later version of Perl and have bugs be fixed without breaking working code. Ruby, not so much.