harmil

I gave a separate answer for Perl 6, but as for Perl 5: Yes, absolutely. I think everyone should know Perl 5 if you ever touch a Linux system. It's installed everywhere and gives you the largest power/keystroke for command-line utility. It's more effective to learn Perl than AWK and Perl has incredibly deep Unicode support and what I call 4th-generation regular expressions (pre-POSIX, POSIX, and then the explosion of early Perl/PCRE/Python-re being the first three and Perl 6's full parser engine being the 5th) which, together, make it like the mythical tool it's often labeled as: the Swiss Army chainsaw.

Don't make the mistake of trying to write anything over a few lines in it, though. You'll find yourself in a deep hole trying to use Moose and "experimental" features just to get back to parity with every other modern language, and you'll still have thin if any support for many modern tools (i.e. those that entirely post-date 2010).

Perl 6 is a great language to learn if your goal is to become a more all-around versed programmer. It has constructs from every major family of programming languages and some features that I've never seen in any other language (NFG strings, operator overloading/declaration with precedence, whatever-code (Lisp has a similar construct), slangs, etc.)

But if you want to learn a programming language that you'll use in your day-to-day job, then unless your day-to-day job is fairly unusual, you won't be using Perl 6. It's fairly slow, very light on surrounding modules unless you want to call out to a Perl 5 compatibility layer and in many modern areas none of the Perl variants have a significant footprint (machine learning comes to mind).

Don't get me wrong. I love the language and program in it daily, but not for work. I write Perl 6 code because I enjoy thinking in highly abstract ways using whatever programming paradigm comes to hand. I write JavaScript, Python, Bash and rarely Java for work.

ntpd guarantees (under the default settings now, though that's new... you can ask it to shoot you in the head, but I don't recommend that you use firearms in this way) that the clock will never go backwards. You're thinking of nptdate, a utility provided with ntpd, but which is only ever supposed to run at system initialization time to get the time close enough for ntpd to take over.

If ntpd finds that the clock is ahead, it will slow the ticks, allowing it to gradually drift back to the correct time.

The system time should NEVER move backwards. Ever. Relying on the system time not moving backwards is not unreasonable for trivialities like how long you wait for a keystroke. If you reset your system time, you might have to hit a key to get vim to wake up. Shucks.