Perl vs perl

The following discussion is an expansion on a question and answer which can be found in the perlfaq1 page of Perl's documentation, namely:
What's the difference between "perl" and "Perl"?
Sometimes you'll see "Perl" written, with a capital P, sometimes "perl", sometimes even PERL.
Confused? Not to worry, Israel.pm to the rescue :-)
The rules are actually quite simple:

• "Perl" should be used when one is writing about the language, for example:
  

  Perl is a language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information. It's also a good language for many system management tasks. The language is intended to be practical (easy to use, efficient, complete) rather than beautiful (tiny, elegant, minimal).

• "perl" should be used when one is writing about the executable which interprets and compiles the Perl code, for example: the perl executable can usually be found at /use/bin/perl on Unix/Linux systems, or on c:\Perl\bin\perl.exe on Windows systems.
• The above two usage forms are not rigidly adhered to, even in Perl's documentation, but in any case you should never use "PERL".
  "PERL" is a backronym, so unless you are going to use it as a joke, don't. It is way overused and abused, and it is time to put it to rest.

There's a famous saying, attributed to Tom Christiansen, which says that Only perl can parse Perl
We'll leave you now to ponder these words of wisdom...

original source : http://perl.org.il/misc.html#pl_vs_pl