37.5 And Now, Perl 5

[This article was adapted from the Perl 5 manual pages. -JP]

Other articles in this chapter were actually written for the previous version, Perl 4, but they apply to Perl 5 as well. Perl 5 is nearly a complete rewrite of Perl 4. Most Perl 4 scripts will work under Perl 5. Perl 5 has these new benefits (and more):

• Many usability enhancements : It is now possible to write much more readable Perl code (even within regular expressions). Error messages are more informative; the optional warnings will catch many of the mistakes a novice might make.

• Lexical scoping : Perl variables may now be declared within a lexical scope, like "auto" variables in C.

• Arbitrarily nested data structures : Any scalar value, including any array element, may now contain a reference to any other variable or subroutine.

• Modularity and reusability : The Perl library is now defined in terms of modules that can be easily shared among various packages. A package may choose to import all or a portion of a module's published interface. Pragmas (that is, compiler directives) are defined and used by the same mechanism.

• Object-oriented programming : A Perl package can function as a class. Dynamic multiple inheritance and virtual methods are supported in a straightforward manner and with very little new syntax. Filehandles may now be treated as objects.

• Embeddable and extensible : Perl may now be embedded easily in your C or C++ application, and can either call or be called by your routines through a documented interface. The XS preprocessor is provided to make it easy to glue your C or C++ routines into Perl. Dynamic loading of modules is supported.

• POSIX compliant : A major new module is the POSIX module, which provides access to all available POSIX routines and definitions, via object classes where appropriate.

• Package constructors and destructors : The new BEGIN and END blocks provide means to capture control as a package is being compiled, and after the program exits. They work just like awk 's BEGIN and END when you use the -p or -n switches.

• Multiple simultaneous DBM implementations : A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB database files from the same script simultaneously.

• Regular expression enhancements : If you thought Perl 4 regular expressions were rich and full of incredible features, wait until you see Perl 5!