From: PerlFAQ Server on
This is an excerpt from the latest version perlfaq1.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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1.12: What's the difference between "perl" and "Perl"?

One bit. Oh, you weren't talking ASCII? :-) Larry now uses "Perl" to
signify the language proper and "perl" the implementation of it, i.e.
the current interpreter. Hence Tom's quip that "Nothing but perl can
parse Perl."

Before the first edition of *Programming perl*, people commonly referred
to the language as "perl", and its name appeared that way in the title
because it referred to the interpreter. In the book, Randal Schwartz
capitalised the language's name to make it stand out better when
typeset. This convention was adopted by the community, and the second
edition became *Programming Perl*, using the capitalized version of the
name to refer to the language.

You may or may not choose to follow this usage. For example, parallelism
means "awk and perl" and "Python and Perl" look good, while "awk and
Perl" and "Python and perl" do not. But never write "PERL", because perl
is not an acronym, apocryphal folklore and post-facto expansions
notwithstanding.



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