This document provides an introduction and overview of the Perl programming language. It discusses the history and uses of Perl, basic Perl syntax and data types, control structures, functions, input/output, and how to use Perl for CGI web development. The key points covered include the origins and popularity of Perl, its pros and cons, how to write "Hello World" programs, define variables and data types, use conditional and loop statements, define and call functions, perform I/O, and generate HTML using CGI.pm for building dynamic web pages and applications with Perl.

1. Programming on the Web(CSC309F)
Tutorial 7: Perl
TA:Wael Abouelsaadat
WebSite: http://www.cs.toronto.edu/~wael
Office-Hour: Friday 12:00-1:00 (SF2110)
Email: wael@cs.toronto.edu
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2. Introduction to Perl
Ø History of Perl!
Ø Initially developed by Larry Wall (English major student then!) in 1987.
Ø Modules continuously added since version 2.0
Ø Latest version is Perl 5.6.1
Ø Ported to 83 platforms.
Ø Most popular “scripting” language for server-side web development.
Ø Pros && Cons:
ü Powerful in manipulating textual data.
ü A very rich set of pattern-matching operations (used extensively in text-searching, NLP systems,…).
ü Rich set of functions (via Perl modules).
ü Allow you to get the job done very quickly (but not necessarily elegantly! ).
û No GUI library.
û Weird syntax (greatly reduces maintainability of Perl progra ms).
Í Perl is an interpreted language.
Í Unix influence (originally built as a replacement for shell scripts and awk).
Ø helloworld.pl
§ Source:
print ( “Hello to Perl World!” );
print “Hello to Perl World!”; # yes, no brackets!
§ Run it:
C:> perl helloworld.pl
Hello to Perl World!Hello to Perl World!
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3. Perl – Data types
Ø Specifying Types and Containers:
§ Variables are not explicitly declared. Perl interpreter guesses the type from the way the variable is written.
$var - names a variable that holds a scalar data type (integer, floating point or string).
@var - names a variable that holds an array of scalars, or list.
%var - names a variable that holds an associative array of scalars.
&var - names a subroutine.
§ E.g.
#Defining a scalar
$Name = "Jack";
$Age = 10;
#Defining and handling an array
@Colors = ("Red","Pink","Yellow");
$FirstColor = $Colors[0];
print( $FirstColor ); # Outputs Red
$Colors[0] = "White";
print( $Colors[0] ); # Outputs White
$Colors[100] = “Blue”; # This is valid because Arrays in Perl are dynamic in size
print( $Colors[100] ); # Outputs Blue
print( $#Colors ); # Prints 100 which is the last index of the array. This is a unique variable
# defined by the perl interpreter to give you access to current size of array
# Defining and handling a hash table
%Address = ("Apartment" => 101,
"Street" => "Bloor",
"City" => "Toronto");
$streetName = $Address{"Street"};
print( $streetName ); # Outputs Bloor
$Address{"City"} = "Ottawa";
print( $Address{"City"} ); # Outputs Ottawa
delete $Address{"City"};
@tkeys = keys(%Address); # keys function returns an array of the keys in the hash table
Ø Global vs. Local variables: 3
§ $Name = “John”; # Visible in the whole program
my $Name = “John”; # Visible in the block it is declared in

4. Perl – Strings
Ø Strings:
§ Difference between using the single quote (') and the double quote (") to delimit strings:
$Client = 'John Luu';
@Items = ( "Chocolate", "Biscuits", "Milk");
$Total = 60;
$Transaction = "$Client is buying @Items for $ $Total";
print( $Transaction ); # Outputs John Luu is buy ing Chocolate Biscuits Milk for $ 60
§ Concatenating Strings:
$FirstName = ‘John'; $LastName = “Black”;
$FullName = $First Name . $LastName ; # FullName is now “John Black”
§ String operators:
# lt: less than , le: less or equal , eq: equal , ge: greater or equal , ne: not equal , eq: equal
$Val1 = ‘1.1’; $Val2 = ‘1.0’;
$Val3 = ‘bbb’; $Val4 = ‘aaa’;
if( ($Val1 gt $Val2) && ($Val3 lt $Val4 ) ) ……………………
§ Pattern matching:
# =~: does match , !~: does not match
$CatString = “tomcat”
if ( $CatString =~ /cat/ ) …. # Right-hand-side of these operators must always be a regular expression
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5. Perl – Control , Loops and Functions
ØControl statements:
§ If statement: Unless Statement
if( $Size < 10.0 ) { unless( $Name eq “John Black” ){
print( "Length is too small!n" ); print( “ You are not John Black” );
} }
elsif ( $Size > 100.0 ) {
print( "Length is too big!n" );
}
else{
print( "Length is just right!n" );
}
Ø Looping:
§ While Loops: For Loops:
while( $n <= 10 ) { for( $n = 1; $n <= 10; ++$n ) {
printf( "%d squared is %dn", $n, $n*$n ); printf( "%d squared is %dn", $n, $n*$n );
$n = $n + 1; }
}
§ For-each Loops:
@Digits = (0,1,2,3,4,5,6,7,8,9);
foreach $n (@Digits) {
printf( "%d squared is %dn", $n, $n*$n );
}
Ø Functions
§ e.g.:
sub func1{
my($param1,$param2) = @_; # parameters are passed in an array called @_
print "Inside func";
$param1 * $param2; # same as return($param1 * $param2 );
}
print(" Before calling func1");
$result = func1( 10,20 ); 5
print(" After calling func1");
print(" result : $result"); # prints result: 200

6. Perl – Functions cont’d
Ø Perl built-in functions:
§ Debugging Functions
# caller( )
# Unwinds the calling stack: ($package, $filename, $line,$SubName , $args,$$contentxt) = caller( $frame );
a( );
sub a { b(); }
sub b { c(); }
sub c { print ( “@{ [ caller(1) ] } “ ); } # Outputs main script.pl 2 main::b 1 0
# die( )
# Kills a process at a given point.
open ( REPORT_FILE, ">report.txt" ) || die " Error opening report.txt $! n " ;
# The above translates to if( open( ….) continue ) else { die …. }
# warn( )
# Does the same thing as die but does not exit.
§ Time Functions
# ($secs , $min, $hr, $mday, $mnth, $yr, $wd, $yd, $ds ) = localtime ( ); Gets local time
# ($user, $system, $child_user, $child_system ) = times( ); Benchmark code
# sleep( $seconds );
§ Variable Functions
# sort(…) Sorts an array in alphabetical order, or by a user-defined function.
@DestArray = ( ‘Apples’, ‘Bananas’, ‘Carrots’ );
@NewArray = sort( @DestArray ); #Be carefull with arrays of numbers
# split(…) Takes a scalar and separates it based on on the criteria us er provides
# @NewArray = split( $text, $ScalarName ); $text can be delimiter or regular expression
@splitArray = spli( “,” , $scalarName );
# grep(…) Finds which element in an array satisfies a condition.
#@NewArray = grep( EXPRESSION , @arrayToMatch );
@Foods = ( ‘turkey’, ‘lucky charms ’, ‘oranges’ ); 6
@longFoods = grep( length($_) > 6 , @foods );

7. Perl – Functions cont’d
# map(…) Makes a new array based on a transform from the old array.
# @NewArray = map( &function, @source_array );
@NewArray = map( MyFunc ( $_ ) , @SourceArray );
§ File Functions
# $bytes = read( FILEHANDLE, $scalar, $length, $offset )
Open( FILEHANDLE, “file” );
$bytes = read( FILEHANDLE, $input, 40, 20 ); # reads 40 characters from file into $input starting at 20
#printf [FILEHANDLE] $format_string, @arrayOfValues;
use FileHandle;
my $Fhandle = new FileHandle( “> my_file” );
$longvarb = “This has 23 chars in it”;
printf $Fhandle “%10.10sn” , $longvarb;
§String Functions
#chop( ) Deletes the last character in a scalar. If applied to Array, hash => does the same!
$line = “ Please chop the letter T”;
chop( $line );
# chomp( ) Deletes the new line character, at the end of the line, if exists.
# More funs: chr, crypt, hex, index, lc, length, oct, ord, pack, reverse, rindex, sprintf, substr, uc, ucfirst
§ Array Functions
#pop, push, shift, splice, unshift
§ Hash Functions
# delete, each, exists, keys, values
§ I/O Functions
# binmode , close, closedir, dbmclose, dbmopen, eof, fileno, flock, format, getc, print, printf, read, readdir,
# rewinddir, seek, seekdir, select, syscall, sysread, sysseek, syswrite, tell, telldir, truncate, write
§ Files/Directories Functions
# -X, chdir, chmod, chown, chroot, fcntl, glob, ioctl, link, lstat, mkdir, open, opendir, readlink, rename,
# rmdir, stat, symlink, umask, unlink, utime
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8. Perl – Input and Output
Ø Printing Output:
§ Standard Output:
print( STDOUT "Hello World!n" );
print( "Hello World! n" );
§ Files:
open( OUT, ">test.dat" ); # Associates file handle with file
print( OUT “ This text will be written in the file " );
ØReading input:
§ Standard Output:
$NewLine = <STDIN>; # Reads one complete line from standard input
$ProgramArguments = <ARGV>; # Refer to arguments on the command line.
# e.g. perl prog param1 param2 param3
§ Files:
open( IN, “<test.dat" ); # Associates file handle with file
$Line = <IN>; # Reads the first line
close( IN );
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9. Perl – Program Structure
Ø Perl Files (.pl) vs Perl Modules (.pm)
File.pl File.pm
§ Where is main()?
ØRequire Statement func1
§ Causes the Perl interpreter to “execute” the code in the require d file!
# foo.pl
func2
perl code
more perl code….
some code
1;
#-----------------------------------------------
# Poo.pl
require “foo.pl”;
perl code # you can call functions in foo.pl
Ø Defining a Perl package and the use statement
§ Semi-Object Oriented Programming! Creates a namespace.
# Student.pm
#!/usr/sbin/perl
package Student;
sub new {
# Initialization code
}
sub printDetails{
# perl code …..
}
#-------------------------------
# foo.pl
use Student; # Like inc lude in C++
$new_student = new Student( );
$new_student->printDetails( );
Ø Another way to use use !
Use CGI qw(); # Uses a specific function in a module: qw 9
Ø use strict;
§ Forces Perl interpreter to be strict in using types. Will save you a lot of time !

10. Perl - CGI
Ø Handling Query String
# dispatcher.pl
use strict;
# Retrieving query string
$request_method = $ENV{‘REQUEST_METHOD’};
if( $request_method eq “GET” ){
$query_string = $ENV{‘QUERY_STRING’};
}
elsif ( $request_method eq “POST” ){
read( STDIN , $query_string, $ENV{‘CONTENT_LENGTH’} );
}
else{
print(“Invalid Request Method !”);
exit( 1 );
}
# Extracting name -value pairs from query string (param1=value1&param2=value2&..…)
@name_value_paris = split( /&/, $query_string );
foreach $name_value (@name_value_pairs){
($name, $value ) = split( /=/, $name_value );
#more Perl code…..
}
Ø Generating HTML
print “Content-type: text/htmlnn”;
print “<html><head> n”;
print “<title> foo title </title></head> n”;
print “<body>”
……………..
Print “</body></html>
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11. Perl - cgi.pm
Ø Using cgi.pm
use strict;
use CGI qw(:standard);
print ( header( ) );
print( start_html( “Anna Web Page” ) ); # <html><head><title>Anna Web Page</title></head><body>
print( table( ….) );
print( a(…) ); # <a href=“”> xyz </a>
print( radio_group(…..) );
print( end_html( ) ); # </body></html>
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12. Assignment 3
Ø What is it about? Client(Web-Browser) Server(HTTP Server)
HTML/ Perl/
Ø What can you do right now? JavaScript/ CGI/
§ HTML (design and layout of the web pages) Cookies Cookies
§ JavaScript (validations)
SMTP POP3
Ø What you need to learn?
§ Perl
§ Cookies
§ CGI SMTP Server POP3 Server
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