If you try to access a key/value pair from a hash in Perl that doesn't exist, you'll normally get the undefined value, and if you have warnings switched on, then you'll get a warning generated at run time. You can get around this by using the exists function, which returns true if the named key exists, irrespective of what its value might be −Example Live Demo#!/usr/bin/perl %data = ('John Paul' => 45, 'Lisa' => 30, 'Kumar' => 40); if( exists($data{'Lisa'} ) ) {    print "Lisa is $data{'Lisa'} years old"; } else {    print "I don't know age of Lisa"; ... Read More

You can get a list of all of the keys from a hash in Perl by using keys function, which has the following syntax −keys %HASHThis function returns an array of all the keys of the named hash. Following is the example −Example Live Demo#!/usr/bin/perl %data = ('John Paul' => 45, 'Lisa' => 30, 'Kumar' => 40); @names = keys %data; print "$names[0]"; print "$names[1]"; print "$names[2]";OutputThis will produce the following result −Lisa John Paul KumarSimilarly, you can use values function to get a list of all the values. This function has the following syntax −Syntaxvalues %HASHThis function returns a normal ... Read More

When accessing individual elements from a hash in Perl, you must prefix the variable with a dollar sign ($) and then append the element key within curly brackets after the name of the variable. For example −Example Live Demo#!/usr/bin/perl %data = ('John Paul' => 45, 'Lisa' => 30, 'Kumar' => 40); print "$data{'John Paul'}"; print "$data{'Lisa'}"; print "$data{'Kumar'}";OutputThis will produce the following result −45 30 40

Perl Hashes are created in one of the two following ways. In the first method, you assign a value to a named key on a one-by-one basis −$data{'John Paul'} = 45; $data{'Lisa'} = 30; $data{'Kumar'} = 40;In the second case, you use a list, which is converted by taking individual pairs from the list: the first element of the pair is used as the key, and the second, as the value. For example −%data = ('John Paul', 45, 'Lisa', 30, 'Kumar', 40);For clarity, you can use => as an alias for, to indicate the key/value pairs as follows −%data = ... Read More

The list notation in Perl is identical to that for arrays. You can extract an element from an array by appending square brackets to the list and giving one or more indices −Example Live Demo#!/usr/bin/perl $var = (5,4,3,2,1)[4]; print "value of var = $var"OutputThis will produce the following result −value of var = 1Similarly, we can extract slices, although without the requirement for a leading @ character −Example Live Demo#!/usr/bin/perl @list = (5,4,3,2,1)[1..3]; print "Value of list = @list";OutputThis will produce the following result −Value of list = 4 3 2

Because an array in Perl is just a comma-separated sequence of values, you can combine them together as shown below −Example Live Demo#!/usr/bin/perl @numbers = (1,3,(4,5,6)); print "numbers = @numbers";OutputThis will produce the following result −numbers = 1 3 4 5 6The embedded arrays just become a part of the main array as shown below −Example Live Demo#!/usr/bin/perl @odd = (1,3,5); @even = (2, 4, 6); @numbers = (@odd, @even); print "numbers = @numbers";OutputThis will produce the following result −numbers = 1 3 5 2 4 6

Perl provides numerous special variables, which have their predefined meaning.We have a special variable, which is written as $[. This special variable is a scalar containing the first index of all arrays. Because Perl arrays have zero-based indexing, $[ will almost always be 0. But if you set $[ to 1 then all your arrays will use on-based indexing. It is recommended not to use any other indexing other than zero. However, let's take one example to show the usage of $[ variable −Example Live Demo#!/usr/bin/perl # define an array @foods = qw(pizza steak chicken burgers); print "Foods: @foods"; # Let's ... Read More

The sort() function in Perl sorts each element of an array according to the ASCII Numeric standards. This function has the following syntax −Syntaxsort [ SUBROUTINE ] LISTThis function sorts the LIST and returns the sorted array value. If SUBROUTINE is specified then specified logic inside the SUBROUTINE is applied while sorting the elements.Example Live Demo#!/usr/bin/perl # define an array @foods = qw(pizza steak chicken burgers); print "Before: @foods"; # sort this array @foods = sort(@foods); print "After: @foods";OutputThis will produce the following result −Before: pizza steak chicken burgers After: burgers chicken pizza steakPlease note that sorting is performed based on ... Read More

We can use the join() function in Perl to rejoin the array elements and form one long scalar string. This function has the following syntax −Syntaxjoin EXPR, LISTThis function joins the separate strings of LIST into a single string with fields separated by the value of EXPR and returns the string. Following is the example −Example Live Demo#!/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 ... Read More

Let's look into a Perl function called split(), which has the following syntax −Syntaxsplit [ PATTERN [ , EXPR [ , LIMIT ] ] ]This function splits a string into an array of strings and returns it. If LIMIT is specified, splits into at most that number of fields. If PATTERN is omitted, splits on whitespace. Following is the example −Example Live Demo#!/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]";    # This will print ... Read More