How do I...
How do I get data from a database?
DBI, and its DBD children, like DBD::SQLite
How do I get data from a web page?
LWP stands for "libwww-perl", and is the standard way of talking to web pages.
WWW::Mechanize is a superset of LWP that makes HTML processing easier.
How do I do date calculations?
Use Date::Manip,
Date::Calc or DateTime.
All have different styles and different capabilities.
How do I handle command-line arguments in my program?
Use Getopt::Long.
How do I write CGI programs?
Use CGI.
How do I parse HTML?
Whatever you do,
don't use regular expressions.
Use HTML::Parser or one of the many classes that uses it.
Look around on http://search.cpan.org.
If you're parsing HTML so that you can extract links or images from a web page,
use WWW::Mechanize which handles it for you.
How do I parse XML?
See the list of Recommended XML Modules at the Perl 5 wiki.
http://www.perlfoundation.org/perl5/index.cgi?recommended_xml_modules
How do I know if a URL is valid?
How do I do screen access?
How do I do colors?
Use Term::ANSIColor. Example wanted.
How do I do readkey? How do I enter passwords without seeing them entered?
Use Term::ReadKey (http://search.cpan.org/dist/TermReadKey). It's a standard core module.
use Term::ReadKey;
ReadMode('noecho');
my $passwd;
my $pwcheck;
print 'password: ';
chomp($passwd = <STDIN>);
print "\n";
print 'verify: ';
chomp($pwcheck = <STDIN>);
print "\n";
ReadMode('normal');
print "You entered [$passwd] and [$pwcheck]\n";