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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1.4: What are perl4, perl5, or perl6?
(contributed by brian d foy)
In short, perl4 is the past, perl5 is the present, and perl6 is the
future.
The number after perl (i.e. the 5 after perl5) is the major release of
the perl interpreter as well as the version of the language. Each major
version has significant differences that earlier versions cannot
support.
The current major release of Perl is perl5, and was released in 1994. It
can run scripts from the previous major release, perl4 (March 1991), but
has significant differences. It introduced the concept of references,
complex data structures, and modules. The perl5 interpreter was a
complete re-write of the previous perl sources.