Slice and Dice - Perl

Perl allows you to extract a subsection of an array - a so-called "array slice" - simply by specifying the index values needed in the slice. Consider the following example:


#!/usr/bin/perl 
# define array 
@rainbow = ("red", "green", "blue", "yellow", "orange", "violet", "indigo");
 
# extract slice "blue", "yellow" 
@slice = @rainbow[2,3]; 



Or how about this one?


#!/usr/bin/perl 
# define array 
@rainbow = ("red", "green", "blue", "yellow", "orange", "violet", "indigo"); 
 
# extract slice "blue", "violet", "red", "indigo" 
@slice = @rainbow[2,5,0,6]; 



You can also use a negative index for the "start" position, to force Perl to begin counting from the right instead of the left.


#!/usr/bin/perl 
# define array 
@rainbow = ("red", "green", "blue", "yellow", "orange", "violet", "indigo"); 
 
# extract slice "indigo", "red" 
@slice = @rainbow[-1,-7]; 



Perl also comes with a range operator (..) which provides an alternative way of extracting array slices. Here's an example:


#!/usr/bin/perl 
# define array 
@rainbow = ("red", "green", "blue", "yellow", "orange", "violet", "indigo"); 
 
# extract elements 2 to 5 
# slice contains "blue", "yellow", "orange", "violet" 
@slice = @rainbow[2..5]; 



You can also use the range operator to create arrays consisting of all the values in a range. For example, if you wanted an array consisting of the numbers between 1 and 20 (both inclusive), you could use the following code to generate it automatically:


#!/usr/bin/perl 
# define array 
@n = (1..20); 



The splice() function allows you to delete a specified segment of an array and splice in one or more values to replace it. Here's what it looks like:


splice(array, start, length, replacement-values) 



where "array" is an array variable, "start" is the index to begin slicing at, "length" is the number of elements to remove from "start", and "replacement-values" are the values to splice in.

Here's an example:


#!/usr/bin/perl 
# define array 
@rainbow = ("red", "green", "blue"); 
 
# remove elements 1 and 2 
# replace with new values 
splice (@rainbow, 1, 2, "yellow", "orange"); 
 
# array now looks like this 
@rainbow = ("red", "yellow", "orange");