Introduction to Perl Programming

Introduction to Perl Programming

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Presentation By Ramananda M.S Rao

ContentContentOverviewGet StartedFunctions & SubroutinesRegular Expressions and PatternsBasic Input and OutputFormatting and ReportingSystem Interaction and ProcessOOPS ConceptsModules ,Packages and NamespacesProjectAbout Us

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OverviewPerl 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.

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Get Started#!/usr/bin/perl# This will print "Hello, World"print "Hello, world\n";#!/usr/bin/perlprint("Hello, world\n");print "Hello, world\n";#!/usr/bin/perlprint "Hello, world\n";print 'Hello, world\n';

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Data Types#!/usr/bin/perl$number = 2; $st1 = ‘one fine $number day’; $st2 = “$number fine day \n”; print $st2; print “$st1\n”;

#!/usr/bin/perl$v1 = 127; $v1 = $v1 . ", and more !!"; # . Indicates to concatenate two dataprint $v1, “\n”; $v1 = 127; print $v1 + "151 ", "\n"; print $v1 + ", and more !!", "\n";

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Data Types#!/usr/bin/perl my @array = (10, 20, 30); # Assign list variables to scalar variablesmy $scalar1; my $scalar2; my $scalar3;($scalar1, $scalar2, $scalar3) = @array;print "Scalar one is $scalar1\n";print "Scalar two is $scalar2\n";print "Scalar three is $scalar3\n";Adding to an Array#!/usr/bin/perl# addelem.pluse warnings; use strict;my @array1 = (1, 2, 3);my @array2 = (@array1, 4, 5, 6);print "@array2\n";@array2 = (3, 5, 7, 9);@array2 = (1, @array2, 11);print "@array2\n";>perl addelem.pl1 2 3 4 5 61 3 5 7 9 11

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

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Functions and Subroutinesfunc2.pl: firstSub(1, 2, 3, 4, 5, 6);firstSub(1..3);firstSub("A".."Z");sub firstSub() { $numParameters = @_ ; print("The number of parameters is $numParameters\n"); }func4.pl|: @array = (0..5);print("Before function call, array = @array\n");firstSub(@array);print("After function call, array = @array\n"); sub firstSub{ $_[0] = "A"; $_[1] = "B";} This program prints: Before function call, array = 0 1 2 3 4 5After function call, array = A B 2 3 4 5}

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

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Modules A module is a package contained within an external

file of the same name.pm extensionfile MyMod.pm:package MyMod; #no shebang!!use strict;use warnings;our ($foo, $bar, $baz);($foo, $bar) = split /\s+/, 'Hello World';$baz = 42;1;

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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::foo\n";prints "Hello World\n"

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