|
Softpanorama
(slightly skeptical)
Open Source Software Educational Society |
May the
source be with you,
but remember the KISS principle ;-)
|
Perl Language
See
Skeptical introduction to Perl for
the introduction.
Notes:
- Those pages are written by people for whom English is not a
native language. Some amount of grammar and spelling errors
should be expected.
- This is a Spartan WHYFF (We Help You For Free) site. It
cannot replace the best teachers and
the
best books.
- The site contain some obsolete pages as it develops like a
living tree... Some links on older pages
are broken. Please
try to use Google, Open directory, etc. to find a replacement link
(see
HOWTO search the WEB for details).
We would appreciate if you can
mail us a correct link.
|
|
[Mar 25, 2006] Beginning
Perl now available in eBook from Perl.com.
This is a very good intro
book!.
In the Beginning, some time around 1960, every part of your program had
access to all the variables in every other part of the program. That turned
out to be a problem, so language designers invented local variables, which
were visible in only a small part of the program. That way, programmers who
used a variable x could be sure that nobody was able to tamper with
the contents of x behind their back. They could also be sure that
by using x they weren't tampering with someone else's variable by
mistake.
Every programming language has a philosophy, and these days most of these
philosophies have to do with the way the names of variables are managed.
Details of which variables are visible to which parts of the program, and
what names mean what, and when, are of prime importance. The details vary
from somewhat baroque, in languages like Lisp, to extremely baroque, in
languages like C++. Perl unfortunately, falls somewhere towards the rococo
end of this scale.
The problem with Perl isn't that it has no clearly-defined system of name
management, but rather that it two systems, both working at once. Here's the
Big Secret about Perl variables that most people learn too late: Perl has
two completely separate, independent sets of variables. One is left
over from Perl 4, and the other is new. The two sets of variables are called
`package variables' and `lexical variables', and they have nothing to do
with each other.
Package variables came first, so we'll talk about them first. Then we'll
see some problems with package variables, and how lexical variables were
introduced in Perl 5 to avoid these problems. Finally, we'll see how to get
Perl to automatically diagnose places where you might not be getting the
variable you meant to get, which can find mistakes before they turn into
bugs.
© Copyright 1998 The Perl Journal.
Reprinted with permission.
One of the most important new features in Perl 5 was the capability to
manage complicated data structures like multidimensional arrays and nested
hashes. To enable these, Perl 5 introduced a feature called `references',
and using references is the key to managing complicated, structured data in
Perl. Unfortunately, there's a lot of funny syntax to learn, and the manual
is not as clear in this area as it usually is. The manual is quite complete,
and a lot of people find that a problem, because it can be hard to tell what
is important and what isn't.
Fortunately, you only need to know 10% of what's in the manual to get 90%
of the benefit. This article is going to show you that 10%.
The B::Xref module is used to generate
a cross reference listing of all definitions and uses of variables,
subroutines and formats in a Perl program. It is implemented as
a backend for the Perl compiler.
The report generated is in the
following format:
File filename1
Subroutine subname1
Package package1
object1 line numbers
object2 line numbers
...
Package package2
...
|
|
Each File section reports on a single file. Each Subroutine
section reports on a single subroutine apart from the special cases
"(definitions)" and "(main)". These report, respectively, on subroutine
definitions found by the initial symbol table walk and on the main
part of the program or module external to all subroutines.
The report is then grouped by the Package of each variable,
subroutine or format with the special case "(lexicals)" meaning
lexical variables. Each object name (implicitly qualified
by its containing Package) includes its type character(s)
at the beginning where possible. Lexical variables are easier to
track and even included dereferencing information where possible.
The line numbers are a comma separated list of line
numbers (some preceded by code letters) where that object is used
in some way. Simple uses aren't preceded by a code letter. Introductions
(such as where a lexical is first defined with my)
are indicated with the letter "i". Subroutine and method calls are
indicated by the character "&". Subroutine definitions are indicated
by "s" and format definitions by "f".
Option words are separated by commas (not whitespace) and follow
the usual conventions of compiler backend options.
-oFILENAME
- Directs output to
FILENAME instead of standard
output.
-r - Raw output. Instead of producing a human-readable report,
outputs a line in machine-readable form for each definition/use
of a variable/sub/format.
-d - Don't output the "(definitions)" sections.
-D[tO] - (Internal) debug options, probably only useful if
-r included. The t option prints the objl&
This plugin causes write attempts to fail if
the contents of the buffer produce an error when
run through "perl -c"
The plugin uses can use autocommands for the BufWriteCmd
and FileWriteCmd events, but by default only provides
a :Write command to check-then-write. |
| |
| install details |
| Put this file in one of the locations described
in :help ftplugin such as "~/.vim/after/ftplugin";
if you want autocommands, which are quirky, define
perl_synwrite_au = 1 |
This is compiler
script that runs perl -Wc and parses all error and
warnings. For more information how to use compilers
in VIM read help.
This version has workaround with redirecting stderr
on windows platform so it can run either on unixes
or windows.
Enjoy. Lukas |
| |
| install
details |
| Just put in the
$VIMRUNTIME/compiler directory and run :make. |
[Dec 26, 2004] http://ppt.perl.org/
Do you know about the Perl Power Tools, at and mirrored various
other places?
It is a great project
to implement versions of standard Unix tools in pure Perl,
so that they can run anywhere Perl does. Those utilities
might be perfect for those who like me I prefer Unix/Linux
as the development platforms, but Windows for my desktop.
They also might be an alternative to the Cygwin stuff even
for those who do not use Perl for own scripting. They should
be the alternative for those who does use Perl. Once Perl
has been installed the PPT stuff only needs to be copied
somewhere and that directory added to the PATH. You can
also learn some great Perl coding tricks by reading the
PPT utilities. Thanks for the anonymous
feedback to the Softpanorama for this info.
Perl has a large number of
command-line options that can help to make your programs
more concise and open up many new possibilities for one-off
command-line scripts using Perl. In this article we'll look
at some of the most useful of these.
Kwiki
The
Kwiki motto
is a "A Quickie Wiki that's not Tricky." Installing it is
pretty straightforward for a site you admin: just install
the Perl package (from CPAN or elsewhere), and then type
kwiki-install in a CGI-served directory to create an instance.
Installing Kwiki
on a server you are not an admin of is more complicated
but doable.
I found the
Kwiki markup not powerful. Some things are impossible
with it, such as hyperlinking an arbitrary piece of text
to an email address (mail fooish). I also
could not find how to link a Wiki page with a text link
different from the Wiki page name (like
this link to LinkedWikiWikiPage).
There is also no support for attachments, HTML markup as
an alternative to the Wiki markup, etc. It is disappointing.
Kwiki can use either RCS
or Subversion for version control. (Those who wish to use
Subversion should
check out the corrected Kwiki
version as the CPAN Kwiki does not work with the up-to-date
Subversion.) Kwiki is easily customizable and has
several Kwiki enhancements available.
Generally, however, they are less powerful than TWiki's.
All in all, Kwiki is easy
to install and customize, but its formatting rules are lacking.
... ... ...
UseModWiki
UseModWiki is a
Wiki engine written in Perl. Anecdotally, Wikipedia used
this first before re-implementing their current engine.
Other sites also use UseModWiki.
UseModWiki is very simple
to set up and upgrade. It has a rich syntax, and allows
for arbitrary characters in page names. It also supports
using some HTML tags instead of the WikiWiki markup. It
has other nice features, including search, a list of recent
changes, and page history.
For simple Wikis, UseModWiki
is a very good choice. I recommend choosing between it and
PmWiki based on the feature list of both Wikis.
In case of broken links
please try to use Google search. If you find the page please notify
us about new location
Several books are available online: see
Perlbooks.
Book chapters
Actually there are few good online tutorials on Perl.
Some Perl Books sites
Please note that all O'Reilly Perl books have one chapter online.
Those chapters are a nice complement to full online books.
Reviews
As for WEB tutorial IMHO only explanation of a particular language
features can probably be useful.
- What is Scalar Context?
-- Every Perl expression is in one of two contexts, either
list context or scalar context, depending on whether it is expected
to produce a list or a scalar. Many expressions have quite different behaviors
in list context than they do in scalar context.
- Perl
objects by Tom Christiansen (1996). Contains rather restrictive and hostile
copyright notice. Not that impressive.
-
switch_statements
- The FMTEYEWTK
series -- Far More Than Everything You've Ever Wanted to
Know About... This series contains a set of documents that address perl-related
certain topic areas in depth. They range from nothing but simple copies of somewhat
lengthy news postings to real, full-blown, htmlified, complete tutorials.
Regular expressions (see special section devoted to this important feature
below)
References
- Understand
References Today -- One of the most important new
features in Perl 5 was the capability to manage complicated data structures
like multidimensional arrays and nested hashes. To enable these, Perl 5 introduced
a feature called `references', and using references is the key to managing complicated,
structured data in Perl. Unfortunately, there's a lot of funny syntax to learn,
and the manual is not as clear in this area as it usually is. The manual is
quite complete, and a lot of people find that a problem, because it can be hard
to tell what is important and what isn't.
General
See also modules, regular
expressions
Copyright © 1996-2008 by Dr. Nikolai Bezroukov.
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Last updated:
June 02, 2008
