The document provides an introduction to the Perl programming language. It discusses that Perl was originally named Pearl and was created by Larry Wall in 1987 as a scripting language for Unix systems. The document outlines the history of Perl versions from 1 to 5.6 and describes key features of Perl like its C-like syntax, dynamic typing, strings, lists, hashes, regular expressions, and object-oriented capabilities. It also discusses how Perl is implemented with an interpreter written in C and how programs are compiled and executed. The document concludes by mentioning the Comprehensive Perl Archive Network which hosts over 114,000 Perl modules.

1. Introduction To PERL Language
Abhishek Pachisia
B.Tech-IT (4th yr)

2. FOREWORD
 Original name Pearl.
 Perl is a high-level, general-purpose, interpreted, dynamic
programming language.
 Perl is a programming language suitable for writing simple
scripts as well as complex applications.
 Perl is not officially an acronym.
 Perl was originally developed by Larry Wall in 1987 as a
general-purpose Unix scripting language
 According to Wall, Perl has two slogans.
 "There's more than one way to do it“.
 "Easy things should be easy and hard things should be
possible"

3. BRIEF HISTORY
 PERL 1 - Released on December 18, 1987.
 PERL 2 - Released in 1988. Better regular
expression engine.
 PERL 3 - Released in 1989. Support for binary
data streams.
 PERL 4 - Released in 1991. To identify the
version.
 Programming Perl -1991. Known as Camel Book.
 PERL 4.036 – Released in 1993.
 CPAN – 26 October, 1995.

4. VERSIONS OF PERL 5
 PERL 5 porters – Released on May,1994.
 PERL 5.000 - October 17,1994. Rewrite of
the interpreter + Many new features.
 PERL 5.001 - March 13,1995.
 PERL 5.002 - February 29,1996. New prototypes
feature
 PERL 5.003 - June 25,1996. Security release.
 PERL 5.004 - May 15,1997.Included UNIVERSAL
package
 PERL 5.005 - July 22,1998.Regex engine
 PERL 5.6 – March 22,2000. 64-bit
support, Unicode string representation etc.

5. SYMBOLS
 Dromedary Camel
 Non-Commercial.
 Onion
 Licenses to its subsidiaries.

6. FEATURES
 The overall structure of Perl derives broadly from C.
 Perl also takes features from shell programming.
 All variables are marked with leading sigils.
 It has many built-in functions.
 Perl takes
 Lists from Lisp,
 Hashes ("associative arrays") from AWK, and
 Regular expressions from sed.

7. FEATURES THAT EASE TASK OF PROGRAMMER
 Automatic memory management,
 Dynamic typing,
 Strings,
 Lists, and hashes,
 Regular expressions,
 Introspection and
 An eval() function.

8. DESIGN - 1
 Response to three broad trends in the computer
industry –
 Falling hardware costs,
 Rising labour costs, and
 Improvements in compiler technology.
 Make efficient use of expensive computer-
programmers.
 No built-in limits similar to the Zero One Infinity rule.
 Syntax reflects the idea that "things that are
different should look different”

9. DESIGN - 2
 Perl favours language constructs that are concise
and natural for humans to write.
 Perl does not enforce any particular programming
paradigm.
 Not a tidy language. Resolve syntactical
ambiguities.
 No written specification/standard through Perl 5
 That interpreter, together with its functional
tests, stands as a de facto specification of the
language.

10. IMPLEMENTATION - 1
 Implemented as a core interpreter, written in C.
 The interpreter is 150,000 lines of C code and
compiles to a 1 MB executable on typical machine
architectures.
 The interpreter has an object-oriented architecture.
 All of the elements are represented in the
interpreter by C structs.
 The life of a Perl interpreter divides broadly into a
compile phase and a run phase.
 In compile phase , Compilation occurs.
 In run phase, Execution occurs.

11. IMPLEMENTATION-2
 At compile time, the interpreter parses Perl code
into a syntax tree.
 At run time, it executes the program by walking the
tree.
 Text is parsed only once, and the syntax tree is
subject to optimization before it is executed.
 It is often said that “Only Perl can parse Perl”.
 Perl makes the unusual choice of giving the user
access to its full programming power in its own
compile phase.
 The cost in terms of theoretical purity is high, but
practical inconvenience seems to be rare.

12. CPAN
 Comprehensive Perl Archive Network.
 An archive of over 114,000 modules of software
written in Perl, as well as documentation for it.
 CPAN can denote
 Archive network itself, or
 The Perl program that acts as an interface to the network
and as an automated software installer
 Most software on CPAN is free and open source
software.
 Components:
 Mirrors
 Search engines
 Testers
 CPAN.pm and CPANPLUS

13. COMPLEX PERL PROGRAM
#!/usr/bin/perl
use strict;
use warnings;
use Time::HiRes qw(sleep time);
use POSIX qw();
use IO::Handle;
my $delay = shift(@ARGV);
STDOUT->autoflush(1);
{
my $start = time();
my $end = $start + $delay;

14. my $last_printed;
while ((my $t = time()) < $end)
{
my $new_to_print = POSIX::floor($end - $t);
if (!defined($last_printed) or $new_to_print !=
$last_printed)
{
$last_printed = $new_to_print;
print "Remaining $new_to_print/$delay", ' '
x 40, "r";
}
sleep(0.1);
}
}
print "n";