Perl cheatsheet

• Open a Web browser and go to https://www.perl.org/get.html.

• Follow the link to download zipped source code available for Unix/Linux.

• Download perl-5.x.y.tar.gz file and issue the following commands at $ prompt.

$tar -xzf perl-5.x.y.tar.gz
$cd perl-5.x.y
$./Configure -de
$make
$make test
$make install

• Follow the link for the Strawberry Perl installation on Windows http://strawberryperl.com

• Download either 32bit or 64bit version of installation.

• Run the downloaded file by double-clicking it in Windows Explorer. This brings up the Perl install wizard, which is really easy to use. Just accept the default settings, wait until the installation is finished, and you're ready to roll!

• Open a Web browser and go to https://www.perl.org/get.html.

• Follow the link to download zipped source code available for Mac OS X.

• Download perl-5.x.y.tar.gz file and issue the following commands at $ prompt

$tar -xzf perl-5.x.y.tar.gz
$cd perl-5.x.y
$./Configure -de
$make
$make test
$make install

# Unix/Linux
$perl  -e <perl code>
# Windows/DOS
C:>perl -e <perl code>

# Unix/Linux
$perl  script.pl
# Windows/DOS
C:>perl script.pl

$perl -e 'print "Hello World\n"'

# #!/usr/bin/perl

# This will print "Hello, World"
print "Hello, world\n";
$chmod 0755 hello.pl
$./hello.pl

# This is a comment in perl
=begin comment
This is all part of multiline comment.
You can use as many lines as you like
These comments will be ignored by the
compiler until the next =cut is encountered.
=cut

#!/usr/bin/perl

# This would print with a line break in the middle
print "Hello
          world\n";
#output
#Hello
#         world

#!/usr/bin/perl

print "Hello, world\n";
print 'Hello, world\n';

#Hello, world
#Hello, world\n$

$age = 25;             # An integer assignment
$name = "John Paul";   # A string
$salary = 1445.50;     # A floating point

#!/usr/bin/perl

$age = 25;             # An integer assignment
$name = "John Paul";   # A string
$salary = 1445.50;     # A floating point

print "Age = $age\n";
print "Name = $name\n";
print "Salary = $salary\n";

#!/usr/bin/perl

@ages = (25, 30, 40);
@names = ("John Paul", "Lisa", "Kumar");

print "\$ages[0] = $ages[0]\n";
print "\$ages[1] = $ages[1]\n";
print "\$ages[2] = $ages[2]\n";
print "\$names[0] = $names[0]\n";
print "\$names[1] = $names[1]\n";
print "\$names[2] = $names[2]\n";

#!/usr/bin/perl

%data = ('John Paul', 45, 'Lisa', 30, 'Kumar', 40);

print "\$data{'John Paul'} = $data{'John Paul'}\n";
print "\$data{'Lisa'} = $data{'Lisa'}\n";
print "\$data{'Kumar'} = $data{'Kumar'}\n";

#!/usr/bin/perl

@names = ('John Paul', 'Lisa', 'Kumar');

@copy = @names;
$size = @names;

print "Given names are : @copy\n";
print "Number of names are : $size\n";

#!/usr/bin/perl

$integer = 200;
$negative = -300;
$floating = 200.340;
$bigfloat = -1.2E-23;

# 377 octal, same as 255 decimal
$octal = 0377;

# FF hex, also 255 decimal
$hexa = 0xff;

print "integer = $integer\n";
print "negative = $negative\n";
print "floating = $floating\n";
print "bigfloat = $bigfloat\n";
print "octal = $octal\n";
print "hexa = $hexa\n";

#!/usr/bin/perl

$var = "This is string scalar!";
$quote = 'I m inside single quote - $var';
$double = "This is inside single quote - $var";

$escape = "This example of escape -\tHello, World!";

print "var = $var\n";
print "quote = $quote\n";
print "double = $double\n";
print "escape = $escape\n";

#!/usr/bin/perl

$str = "hello" . "world";       # Concatenates strings.
$num = 5 + 10;                  # adds two numbers.
$mul = 4 * 5;                   # multiplies two numbers.
$mix = $str . $num;             # concatenates string and number.

print "str = $str\n";
print "num = $num\n";
print "mul = $mul\n";
print "mix = $mix\n";

#!/usr/bin/perl

$string = 'This is
a multiline
string';

print "$string\n";

##########################
print <<EOF;
This is
a multiline
string
EOF

#!/usr/bin/perl

$smile  = v9786;
$foo    = v102.111.111;
$martin = v77.97.114.116.105.110;

print "smile = $smile\n";
print "foo = $foo\n";
print "martin = $martin\n";

#!/usr/bin/perl

print "File name ". __FILE__ . "\n";
print "Line Number " . __LINE__ ."\n";
print "Package " . __PACKAGE__ ."\n";

# they can not be interpolated
print "__FILE__ __LINE__ __PACKAGE__\n";

#!/usr/bin/perl

@var_10 = (1..10);
@var_20 = (10..20);
@var_abc = (a..z);

print "@var_10\n";   # Prints number from 1 to 10
print "@var_20\n";   # Prints number from 10 to 20
print "@var_abc\n";  # Prints number from a to z

#!/usr/bin/perl

@array = (1,2,3);
$array[50] = 4;

$size = @array;
$max_index = $#array;

print "Size:  $size\n";
print "Max Index: $max_index\n";

#!/usr/bin/perl

# create a simple array

@coins = ("Quarter","Dime","Nickel");
print "1. \@coins = @coins\n";

# add one element at the end of the array

push(@coins, "Penny");
print "2. \@coins = @coins\n";

# add one element at the beginning of the array

unshift(@coins, "Dollar");
print "3. \@coins = @coins\n";

# remove one element from the last of the array.

pop(@coins);
print "4. \@coins = @coins\n";

# remove one element from the beginning of the array.

shift(@coins);
print "5. \@coins = @coins\n";

#!/usr/bin/perl

@days = qw/Mon Tue Wed Thu Fri Sat Sun/;

@weekdays = @days[3,4,5];

print "@weekdays\n";

#!/usr/bin/perl

@nums = (1..20);
print "Before - @nums\n";

splice(@nums, 5, 5, 21..25);
print "After - @nums\n";

#!/usr/bin/perl

# define Strings

$var_string = "Rain-Drops-On-Roses-And-Whiskers-On-Kittens";
$var_names = "Larry,David,Roger,Ken,Michael,Tom";

# transform above strings into arrays.

@string = split('-', $var_string);
@names = split(',', $var_names);

print "$string[3]\n";  # This will print Roses
print "$names[4]\n"; # This will print Michael

#!/usr/bin/perl

# define Strings
$var_string = "Rain-Drops-On-Roses-And-Whiskers-On-Kittens";
$var_names = "Larry,David,Roger,Ken,Michael,Tom";

# transform above strings into arrays.
@string = split('-', $var_string);
@names  = split(',', $var_names);

$string1 = join( '-', @string );
$string2 = join( ',', @names );

print "$string1\n";
print "$string2\n";

#!/usr/bin/perl

# define an array
@foods = qw(pizza steak chicken burgers);
print "Before: @foods\n";

# sort this array
@foods = sort(@foods);
print "After: @foods\n";

#!/usr/bin/perl

# define an array
@foods = qw(pizza steak chicken burgers);
print "Foods: @foods\n";

# Let's reset first index of all the arrays.
$[ = 1;

print "Food at \@foods[1]: $foods[1]\n";
print "Food at \@foods[2]: $foods[2]\n";

#!/usr/bin/perl

@odd = (1,3,5);
@even = (2, 4, 6);

@numbers = (@odd, @even);

print "numbers = @numbers\n";

#!/usr/bin/perl

@list = (5,4,3,2,1)[1..3];

print "Value of list = @list\n";

#!/usr/bin/perl

%data = ('John Paul' => 45, 'Lisa' => 30, 'Kumar' => 40);

print "$data{'John Paul'}\n";
print "$data{'Lisa'}\n";
print "$data{'Kumar'}\n";

#!/uer/bin/perl


%data = (-JohnPaul => 45, -Lisa => 30, -Kumar => 40);

@array = @data{-JohnPaul, -Lisa};

print "Array : @array\n";

#!/usr/bin/perl

%data = ('John Paul' => 45, 'Lisa' => 30, 'Kumar' => 40);

@names = keys %data;

print "$names[0]\n";
print "$names[1]\n";
print "$names[2]\n";

#!/usr/bin/perl

%data = ('John Paul' => 45, 'Lisa' => 30, 'Kumar' => 40);

@keys = keys %data;
$size = @keys;
print "1 - Hash size:  is $size\n";

@values = values %data;
$size = @values;
print "2 - Hash size:  is $size\n";

#!/usr/bin/perl

%data = ('John Paul' => 45, 'Lisa' => 30, 'Kumar' => 40);
@keys = keys %data;
$size = @keys;
print "1 - Hash size:  is $size\n";

# adding an element to the hash;
$data{'Ali'} = 55;
@keys = keys %data;
$size = @keys;
print "2 - Hash size:  is $size\n";

# delete the same element from the hash;
delete $data{'Ali'};
@keys = keys %data;
$size = @keys;
print "3 - Hash size:  is $size\n";

#!/usr/bin/perl

# Perl program to illustrate
# Decision-Making statements

$a = 10;
$b = 15;

# if condition to check
# for even number
if($a % 2 == 0 )
{
	printf "Even Number";
}

# if-else condition to check
# for even number or odd number
if($b % 2 == 0 )
{
	printf "\nEven Number";
}
else
{
	printf "\nOdd Number";
}

#!/usr/local/bin/perl

$name = "Ali";
$age = 10;

$status = ($age > 60 )? "A senior citizen" : "Not a senior citizen";

print "$name is  - $status\n";

#!/usr/bin/perl

# Perl program to illustrate
# the use of for Loop

# for loop
print("For Loop:\n");
for ($count = 1 ; $count <= 3 ; $count++)
{
	print "GeeksForGeeks\n"
}

#!/usr/bin/perl

# Perl program to illustrate
# the use of foreach Loop

# Array
@data = ('GEEKS', 4, 'GEEKS');

# foreach loop
print("For-each Loop:\n");
foreach $word (@data)
{
	print ("$word ");
}

#!/usr/bin/perl

# Perl program to illustrate
# the use of foreach Loop

# while loop
$count = 3;

print("While Loop:\n");
while ($count >= 0)
{
	$count = $count - 1;
	print "GeeksForGeeks\n";
}

print("\ndo...while Loop:\n");
$a = 10;

# do..While loop
do {

	print "$a ";
	$a = $a - 1;
} while ($a > 0);

#!/usr/bin/perl

# Perl Program for creation of a
# Class and its object
use strict;
use warnings;

package student;

# constructor
sub student_data
{

	# shift will take package name 'student'
	# and assign it to variable 'class'
	my $class_name = shift;
	my $self = {
				'StudentFirstName' => shift,
				'StudentLastName' => shift
			};
	# Using bless function
	bless $self, $class_name;

	# returning object from constructor
	return $self;
}

# Object creating and constructor calling
my $Data = student_data student("Geeks", "forGeeks");

# Printing the data
print "$Data->{'StudentFirstName'}\n";
print "$Data->{'StudentLastName'}\n";

#!/usr/bin/perl

# Perl Program to demonstrate the
# subroutine declaration and calling

# defining subroutine
sub ask_user
{
	print "Hello Geeks!\n";
}

# calling subroutine
# you can also use
# &ask_user();
ask_user();

#!/usr/bin/perl

# Using the Package 'Calculator'
use Calculator;

print "Enter two numbers to multiply";

# Defining values to the variables
$a = 5;
$b = 10;

# Subroutine call
Calculator::multiplication($a, $b);

print "\nEnter two numbers to divide";

# Defining values to the variables
$a = 45;
$b = 5;

# Subroutine call
Calculator::division($a, $b);

# Perl program to illustrate the
# Referencing and Dereferencing
# of an Array

# defining an array
@array = ('1', '2', '3');

# making an reference to an array variable
$reference_array = \@array;

# Dereferencing
# printing the value stored
# at $reference_array by prefixing
# @ as it is a array reference
print @$reference_array;

# Perl program to demonstrate
# the m// and =~ operators

# Actual String
$a = "GEEKSFORGEEKS";

# Prints match found if
# its found in $a
if ($a =~ m[GEEKS])
{
	print "Match Found\n";
}

# Prints match not found
# if its not found in $a
else
{
	print "Match Not Found\n";
}

# Opening the file
open(fh, "GFG2.txt") or die "File '$filename' can't be opened";

# Reading First line from the file
$firstline = <fh>;
print "$firstline\n";

#!/usr/bin/perl

# Using predefined modules
use warnings;
use strict;

# Providing path of file to a variable
my $filename = 'C:\Users\GeeksForGeeks\GFG.txt';

# Checking for the file existence
if(-e $filename)
{

	# If File exists
	print("File $filename exists\n");
}

else
{

	# If File doesn't exists
	print("File $filename does not exists\n");
}

#!/usr/bin/perl
use Excel::Writer::XLSX;

my $Excelbook = Excel::Writer::XLSX->new( 'GFG_Sample.xlsx' );
my $Excelsheet = $Excelbook->add_worksheet();

$Excelsheet->write( "A1", "Hello!" );
$Excelsheet->write( "A2", "GeeksForGeeks" );
$Excelsheet->write( "B1", "Next_Column" );

$Excelbook->close;

use 5.016;
use Spreadsheet::Read qw(ReadData);
my $book_data = ReadData (‘new_excel.xlsx');
say 'A2: ' . $book_data->[1]{A2};

if(open(DATA, $file)) {
   ...
} else {
   die "Error: Couldn't open the file - $!"
}
#example
open(DATA, $file) || die "Error: Couldn't open the file $!";
## example
unless(chdir("/etc")) {
   die "Error: Can't change directory - $!";
}
##example
print(exists($hash{value}) ? 'There' : 'Missing',"\n");

chdir('/etc') or warn "Can't change directory";

chdir('/etc') or die "Can't change directory";

package T;

require Exporter;
@ISA = qw/Exporter/;
@EXPORT = qw/function/;
use Carp;

sub function {
   warn "Error in module!";
}
1;
#use T;
#function();
# all below code call the funtion

package T;

require Exporter;
@ISA = qw/Exporter/;
@EXPORT = qw/function/;
use Carp;

sub function {
   carp "Error in module!";
}
1;

package T;

require Exporter;
@ISA = qw/Exporter/;
@EXPORT = qw/function/;
use Carp qw(cluck);

sub function {
   cluck "Error in module!";
}
1;

package T;

require Exporter;
@ISA = qw/Exporter/;
@EXPORT = qw/function/;
use Carp;

sub function {
   croak "Error in module!";
}
1;

package T;

require Exporter;
@ISA = qw/Exporter/;
@EXPORT = qw/function/;
use Carp;

sub function {
   confess "Error in module!";
}
1;

#!/usr/local/bin/perl

@months = qw( Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec );
@days = qw(Sun Mon Tue Wed Thu Fri Sat Sun);

($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime();
print "$mday $months[$mon] $days[$wday]\n";
#or
#!/usr/local/bin/perl

$datestring = localtime();
print "Local date and time $datestring\n";

#!/usr/local/bin/perl

$datestring = gmtime();
print "GMT date and time $datestring\n";

#!/usr/local/bin/perl

($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime();

printf("Time Format - HH:MM:SS\n");
printf("%02d:%02d:%02d", $hour, $min, $sec);

#!/usr/local/bin/perl

$epoc = time();

print "Number of seconds since Jan 1, 1970 - $epoc\n";
#or
#!/usr/local/bin/perl

$datestring = localtime();
print "Current date and time $datestring\n";

$epoc = time();
$epoc = $epoc - 24 * 60 * 60;   # one day before of current date.

$datestring = localtime($epoc);
print "Yesterday's date and time $datestring\n";

#!/usr/local/bin/perl
use POSIX qw(strftime);

$datestring = strftime "%a %b %e %H:%M:%S %Y", localtime;
printf("date and time - $datestring\n");

# or for GMT formatted appropriately for your locale:
$datestring = strftime "%a %b %e %H:%M:%S %Y", gmtime;
printf("date and time - $datestring\n");