Perl Programming

TopicsIntroduction to PerlVariables

ScalarsArraysHashes

Regular Expressions

IntroductionPerl – Practical Extraction and Reporting

LanguageDeveloped in 1987 by Larry WallFilenames should have the extension of .plRuns under windows and linuxThe first line of perl under linux is

#!/usr/bin/perlThe first line of perl under windows is

#!c:/perl/bin/perl.exe

IntroductionPerl scripts are interpreted in the command

or shell prompt and even in the browser. If it in the browser, a Http header should be

set likeprint “Content-type: text/html \n\n”;

First example#! C:/perl/bin/perl.exeprint “Content-type: text/html \n\n”;Print “Hello World “;

IntroductionGo to the command prompt and execute the

command perl filename.pl

In the browser, type http://localhost/filename.pl

Perl VariablesScalars ($)

Numbers or Strings or referenceStarted with a $ symbol Ex. $string=“Hello “; $a=200; $x=2**3;

Arrays (@)List of scalar dataDefined by an @ symbol@s=(“hello”, ”world”);

Hashes (%)Complex list with both a key and a value part for each

element of the list.Defined by a % symbol%ages = ("Jerry", 45, "Tom", 22, "Vickie", 38);

Scalars$x = 12345; # integer $x = 12345.67; # floating point $x = 6.02e23; # scientific notation $x = 4_294_967_296; # underline for legibility $x = 0377; # octal $x = 0xffff; # hexadecimal $x = 0b1100_0000; # binary$x=“Hello” # string literalsDouble quotes – variables are interpolatedSingle quotes – variables are not interpolated

Arrays@a=(“hi”,”Hello”,”there”);Print @a;$c=pop @a; # last element “there” is stored

in cPush(@a,”here”);Print @a;Print $a[0]; #index starts at 0, so prints hi

HashesUses a key value pairKey is usually a string literalExample

%hash=(“Tom”,33,”mike”,23,”john”,19);Print %hash;@k=keys %hash;@v=values %hash;$count=keys %hash;While(($keys=>$values)=each %hash){print “$keys=>$values”.”<br/>”;}

Regular ExpressionMatches a word or a phrase or even a

character trying to match a patternMeta charactersPattern Modifiers