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\begin{document}
\begin{center}
\textbf{{\LARGE{}An Overview of Perl}}
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\begin{center}
{\large{}A language for Systems and Network Administration and Management:}
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\begin{center}
{\large{}An overview of the language}
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\textbf{{\LARGE{}Where do I get Perl?}}
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{\Large{}For Windows, go to http://www.activestate.com, download the installer}
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{\Large{}For Linux: it will be already installed}
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{\Large{}For other platforms: go to http://www.perl.com}
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{\large{}This is a good source of other information about Perl}
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\textbf{{\LARGE{}Where do I get Info about Perl?}}
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{\footnotesize{}Web sites:}
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{\large{}http://www.perl.com}
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{\large{}http://www.activestate.com}
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{\large{}http://use.perl.org}
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{\footnotesize{}On your hard disk:}
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{\footnotesize{}perldoc --f }\textit{{\footnotesize{}function}}
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{\scriptsize{}Will look up the documentation for the built-in }\textit{{\scriptsize{}function}}{\scriptsize{} (from the documentation perlfunc)}
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{\footnotesize{}perldoc --q }\textit{{\footnotesize{}word}}
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{\scriptsize{}Will look up }\textit{{\scriptsize{}word}}{\scriptsize{} in the headings of the FAQ}
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{\footnotesize{}perldoc perl}
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{\scriptsize{}A list of much of your locally installed documentation, divided into topics}
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{\footnotesize{}ActiveState Perl provides a Programs menu item that links to online html documentation}
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\textbf{{\LARGE{}CPAN, PPM: Many Modules}}
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A very strong feature of Perl is the community that supports it
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There are tens of thousands of third party modules for many, many purposes:
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{\footnotesize{}Eg. Net::LDAP module supports all LDAP operations, Net::LWP provides a comprehensive web client}
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Installation is easy:
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\begin{flushleft}
\textbf{	sudo perl --MCPAN --e shell}
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\textbf{	install Net::LDAP}
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Will check if a newer version is available on the Internet from CPAN, and if so, download it, compile it, test it, and if it passes tests, install it.
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\textbf{{\LARGE{}PPM: Perl Package Manager}}
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{\large{}For Windows}
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{\large{}Avoids need for a C compiler, other development tools}
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{\large{}Download precompiled modules from ActiveState and other sites, and install them:}
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\textbf{{\large{}ppm install Net::LDAP}}
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{\large{}See documentation with ActiveState Perl}
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\textbf{{\LARGE{}Mailing Lists: help from experts}}
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{\Large{}There are many mailing lists and newsgroups for Perl}
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\begin{flushleft}
{\Large{}When subscribe to mailing list, receive all mail from list}
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{\Large{}When send mail to list, all subscribers receive}
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{\Large{}For Windows, many lists at http://www.activestate.com}
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\textbf{{\LARGE{}How to ask Questions on a List}}
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I receive many email questions from students about many topics
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Most questions are not clear enough to be able to answer in any way except, ``please tell me more about your problem''
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Such questions sent to mailing lists are often unanswered
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Need to be concise, accurate, and clear
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{\footnotesize{}see also Eric Raymond's }\textit{{\footnotesize{}How to Ask Questions the Smart Way}}{\footnotesize{} at }{\large{}http://catb.org/\~{}esr/faqs/smart-questions.html}{\footnotesize{} }
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Search the FAQs first
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\begin{flushleft}
\textbf{{\LARGE{}Where is Perl on my system?}}
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{\Large{}ActiveState Perl installs }\textbf{{\Large{}perl.exe}}{\Large{} in }\textbf{{\Large{}C:\ensuremath{\backslash}Perl\ensuremath{\backslash}perl.exe}}
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{\Large{}Linux systems have a standard location for perl at }\textbf{{\Large{}/usr/bin/perl}}
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{\Large{}On some UNIX systems, it may be installed at }\textbf{{\Large{}/usr/local/bin/perl}}
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\textbf{{\LARGE{}How does my OS know it's a Perl program?}}
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{\footnotesize{}To run your Perl program, OS needs to call perl}
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{\footnotesize{}How does OS know when to call Perl?}
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{\footnotesize{}Windows:}
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{\footnotesize{}OS uses the extension of the file to decide what to do (e.g., }\textbf{{\footnotesize{}.bat}}{\footnotesize{}, }\textbf{{\footnotesize{}.exe}}{\footnotesize{})}
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{\footnotesize{}Your program names end with }\textbf{{\footnotesize{}.pl}}
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{\footnotesize{}Linux, Unix:}
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{\footnotesize{}programs have }\textit{{\footnotesize{}execute}}{\footnotesize{} permission (}\textbf{{\footnotesize{}chmod +x }}\textbf{\textit{{\footnotesize{}program}}}{\footnotesize{})}
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{\footnotesize{}OS reads first 2 bytes of program: if they are ``}\textbf{{\footnotesize{}\#!}}{\footnotesize{}'' then read to end of line, then use that as the interpreter}
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{\footnotesize{}OS doesn't care what your program file is called}
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{\footnotesize{}For cross platform support:}
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\begin{flushleft}
{\footnotesize{}Put this at the top of all your programs:}
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\textbf{{\footnotesize{}\#! /usr/bin/perl --w}}
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{\footnotesize{}Name your programs with an extension }\textbf{{\footnotesize{}.pl}}
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\begin{center}
\textbf{{\LARGE{}Language Overview}}
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\begin{center}
{\large{}A quick look at more important features of the language}
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\begin{flushleft}
\textbf{{\LARGE{}Funny Characters \$, @, \%}}
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\begin{flushleft}
Variables in Perl start with a \textit{funny character}
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Why?
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No problem with reserved words:
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{\footnotesize{}can have a variable called \$while, and another variable called @while, and a third called \%while.}
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Can \textit{interpolate} value into a string:
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\begin{flushleft}
\textbf{{\footnotesize{}my \$string = ``long'';}}
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\begin{flushleft}
\textbf{{\footnotesize{}my \$number = 42.42;}}
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\textbf{{\footnotesize{}print ``my string is \$string and my number is \$number\ensuremath{\backslash}n'';}}
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\begin{flushleft}
\textbf{{\LARGE{}Arrays}}
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\begin{flushleft}
Define an array like this:
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\begin{flushleft}
my @array = ( 1, 5, ``fifteen'' );
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This is an array containing three elements
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The first can be accessed as \$array[0], second as \$array[1], the last as \$array[2]
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\begin{flushleft}
Note that since each element is a scalar, it has the \$ funny character for a scalar variable \textit{value}
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In Perl, we seldom use an array with an index---use list processing array operations
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{\footnotesize{}higher level.}
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\textbf{{\LARGE{}Hashes}}
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Hashes are probably new to you
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Like an array, but indexed by a string
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Similar idea was implemented in java.lang.HashTable
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{\footnotesize{}Perl hashes are easier to use}
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Example:
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\begin{flushleft}
\textbf{my \%hash = ( NL => 'Netherlands',}
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\textbf{			   BE => 'Belgium' );}
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This creates a hash with two elements
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 first is \$hash\{NL\}, has value ``Netherlands'';
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second is \$hash\{BE\} with value "Belgium"
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\textbf{{\LARGE{}String Operations}}
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Perl has all the operators from C, in same precedence
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Has more operators for strings:
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Join strings with a dot, e.g.
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\textbf{{\footnotesize{}	print "The sum of 3 and 4 is " . 3 + 4 . "\ensuremath{\backslash}n";}}
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Quote special characters with a backslash, as in C
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\textbf{	print "\ensuremath{\backslash}\$value = \$value\ensuremath{\backslash}n";}
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Can quote all characters using single quotes:
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\begin{flushleft}
\textbf{{\scriptsize{}	print 'output of \$perl = "rapid";print \$perl; is "rapid"';}}
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Note that double quotes are okay in single quotes, single quotes okay in double quotes.
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\textbf{{\LARGE{}See the perl summary}}
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{\Large{}The Perl summary on the subject web site provides\ldotswell, a good summary!}
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