You can download Perl for free from http://www.perl.org. Read the README and
INSTALL files and do what they say. Once it is installed on a Unix
system, you have an online manual. perldoc
perldoc explains how the manual system works.
perldoc
-f
print, for example, explains how the function
print works; perldoc -q
print finds “print”
in the Perl FAQ.
A simple Perl script looks like this:
#! /usr/local/bin/perl -wT use strict; print "Hello world\n";
The first line, the “shebang” line,
loads the Perl interpreter (which might also be in
/usr/bin/perl) with the -wT
flag, which invokes warnings and checks incoming data for
“taint.” Tainted data could have
come from Bad Guys and contain malicious program in disguise.
-T makes sure you have always processed everything
that comes from “outside” before
you use it in any potentially dangerous functions. For a fuller
explanation of a complicated subject, see Programming Perl by Larry
Wall, Jon Orwant, and Tom Christiansen (O’Reilly,
2000). There isn’t any input here, so
-T is not necessary, but it’s a
good habit to get into.
The second line loads the strict pragma: it imposes a discipline on your code that is essential if you are to write scripts for the Web. The third line prints “Hello world” to the screen.
Having written this, saved it as hello.pl and
made it executable with chmod +x hello.pl, you can
run it by typing ./hello.pl.
Whenever you write a new script or alter an old one, you should
always run it from the command line first to detect syntax errors.
This applies even if it will normally be run by Apache. For instance,
take the trailing " off the last line of
hello.pl, and run it again:
Can't find string terminator '"' anywhere before EOF at ./hello.pl line 4