Introduction to Perl Programming

Introduction to Perl Programming
www.collaborationtech.co.in
Bengaluru INDIA
Presentation By
Ramananda M.S Rao

Content
Content
Overview
Get Started
Functions & Subroutines
Regular Expressions and Patterns
Basic Input and Output
Formatting and Reporting
System Interaction and Process
OOPS Concepts
Modules ,Packages and Namespaces
Project
About Us

Overview
 Perl is an interpreted language, meaning that a control
program that understands the semantics of the language
and its components (the interpreter) executes program
components individually as they are encountered in the
control flow.
 Interpreted execution makes Perl flexible, convenient,
and fast for programming, with some penalty paid in
execution speed.
 Perl programs are often called scripts because of its
historical development as an extension of the Unix
command-level command scripting notations.

Get Started
#!/usr/bin/perl
# This will print "Hello, World"
print "Hello, worldn";
#!/usr/bin/perl
print("Hello, worldn");
#!/usr/bin/perl
print 'Hello, worldn';

Data Types
#!/usr/bin/perl
$number = 2;
$st1 = ‘one fine $number day’;
$st2 = “$number fine day n”;
print $st2; print “$st1n”;
#!/usr/bin/perl
$v1 = 127;
$v1 = $v1 . ", and more !!"; # . Indicates to concatenate two data
print $v1, “n”;
$v1 = 127; print $v1 + "151 ", "n";
print $v1 + ", and more !!", "n";

Data Types
#!/usr/bin/perl
my @array = (10, 20, 30);
# Assign list variables to scalar variables
my $scalar1; my $scalar2; my $scalar3;
($scalar1, $scalar2, $scalar3) = @array;
print "Scalar one is $scalar1n";
print "Scalar two is $scalar2n";
print "Scalar three is $scalar3n";
Adding to an Array
#!/usr/bin/perl
# addelem.pl
use warnings; use strict;
my @array1 = (1, 2, 3);
my @array2 = (@array1, 4, 5, 6);
print "@array2n";
@array2 = (3, 5, 7, 9);
@array2 = (1, @array2, 11);
print "@array2n";
>perl addelem.pl
1 2 3 4 5 6
1 3 5 7 9 11

Control Structure
If / elsif / else
if ($thresh < 10) {
# … the ‘then’ block of the conditional
} elsif ($thresh < 20) {
# the next block in the decision tree
} elsif ($thresh < 40) {
# and the next…
} else {
# the final clause catches what falls through
}
#!/usr/bin/perl
# conditional.pl
use strict; use warnings;
my ($x, $y) = @ARGV;
if ($x == $y) { print "equaln"; }
else { print "not equaln"; }

Functions and Subroutines
func2.pl:
firstSub(1, 2, 3, 4, 5, 6);
firstSub(1..3);
firstSub("A".."Z");
sub firstSub() {
$numParameters = @_ ;
print("The number of parameters is $numParametersn");
}
func4.pl|:
@array = (0..5);
print("Before function call, array = @arrayn");
firstSub(@array);
print("After function call, array = @arrayn");
sub firstSub{ $_[0] = "A"; $_[1] = "B";}
This program prints:
Before function call, array = 0 1 2 3 4 5
After function call, array = A B 2 3 4 5}

Functions and Subroutines
#!/usr/bin/perl
# gc.pl
use strict; use warnings;
while (my $seq = <>) {
chomp($seq);
gc($seq); 8. }
sub gc {
my ($seq) = @_;
$seq = uc($seq); # convert to upper case to be sure
my $g = $seq =~ tr/G/G/;
my $c = $seq =~ tr/C/C/;
my $gc = ($g + $c) / length($seq);
print "GC% = $gcn";
} };

Modules
 A module is a package contained within an external
file of the same name
.pm extension
file MyMod.pm:
package MyMod; #no shebang!!
use strict;
use warnings;
our ($foo, $bar, $baz);
($foo, $bar) = split /s+/,
'Hello World';
$baz = 42;
1;

Packages
#!/usr/bin/perl
use warnings; #note no use strict!
$foo = 'Hello'; #sets $main::foo
package Bar;
$foo = 'World'; #sets $Bar::foo
package Lalli;
print "$main::foo $Bar::foon";
prints "Hello Worldn"

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Introduction to Perl Programming

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