Day 1: Tutorials: Advanced Perl Programming

Tom Christiansen has been using Perl since its first versions and has been teaching perl since 1989. In other words, it's a subject he knows a little bit about

. Besides, on top of obviously being a knowledgeable speaker, Tom is a fun speaker just like Larry (Wall, although it's also true of Larry McVoy)

The interesting thing is that he wrote his slides in troff macros, which get parsed by a few programs of his and end up in postscript, but then I also found out that the perl books were written in perldoc, and troff where perldoc wasn't enough. A book in perldoc, pfheww...

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Here are a few random bits from his tutorial (I hope I didn't mess anything up):

%Foo:: is the hash of variables in package Foo
INIT is called automatically just like BEGIN in a package, but it's just before running the package, not at the time it is compiled. To have the whole file in scope, INIT can be put at the end of the file.
use sigtrap lets you trap an exception like a signal so that END isn't called
do $file will run a file located in the @INC search path while the ugly `cat $file` will not use the @INC path, requires a cat binary and puts the file in the local scope
use Fcntl () works like require Fcntl except that it happens at compile time, and use also allows for function signatures, if there are any, to be checked for consistency.
require $file works like do $file, but each loaded file is stored in the %INC path so that it's never loaded twice (no if defined file_h hack, like in C header files)
file.pl is a perl library, so that extension shouldn't be used for perl executables
A package name shouldn't be all lower case because those names are reserved by perl.
Carp is nice for error reporting. carp is like warn, and croak is like die, but they report an error message from the caller perspective. You also have confess and cluck which give a full stack backtrace.
ref $var returns the type of variable that $var is a reference to
Perl tends to overallocate memory grossly (next power of two) which can be an issue for multidimensional arrays, so you should be prepared to have up to 10 times more memory than needed (maybe more). There are also CPAN modules that are designed to handle multidimensional data structures more efficiently (those are usually written in C).
Tom read some perl book where ISA (from @ISA) stood for Industry Standard Architecture

Another well known Perl hacker, Chip, was in the audience and helped answer a few questions at the end.

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99/08/09 (22:20): Version 1.0
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