Perl Data TypesNEW!!! Check my new resource: Perl How To Tutorial eBooks There are three built-in Perl Data Types: scalars, arrays and hash or associative arrays, that make the Perl language a powerful tool for text manipulation. 1. The first type of Perl data types is the scalar which is Perl’s data fundamental unit and it can be a single string, a number or a reference to a specific object. When we speak about scalars, we have in view two types:
The name of a variable can contain any alphabetic characters, numbers or underscore. Note that the first character of a scalar variable name can’t be a number and the variable names are case sensitive, which means there is a significant difference between upper and lowercase characters. In Perl language it’s not necessary to declare a scalar variable, you just name and use it like in this scalar variable assignment example: Check my new How To Tutorial eBooks (PDF format):
to see a lot of fully commented examples that help you use the Perl built-in functions and the Perl statements in your scripts. In a scalar variable we can store the memory address of a chunk of memory, too. We call reference the scalar value that contains a memory address. Perl allocates and deallocates automatically the memory for references. Look at the following code snippet to see how you can use a reference variable: In the first line of code, the variable named $a stores the string “Hello World”. In the second line, the scalar variable ref_a is assigned with a reference to the variable $a (note that $a is preceded by the character \). The third line of the snippet is an example of how to print the string stored in the variable $a using a reference – we say that we dereference the scalar variable $ref_a before print. It’s a good practice to name a scalar reference beginning with the substring ref_, because this will tell you that this is a reference variable and if you want to use it, you must dereference it before. Another kind of constants are literal lists which are used to initialize an array or a hash. To create a literal list it is very easy, just put a set of parentheses enclosing scalar values as in the following example: where we can see a list with 4 elements. 2. The second basic type of the Perl data types is the array which is indexed by a number. For creating an array you simple must put something into it. It is not necessary to declare or specify its dimension. The name of an array begins with the character @ and in the example below we will assign the array @things with the literal list presented above: 3. The third basic type of the Perl data types is the hash or associative array, which, like the array, contains a number of scalars. Hashes are indexed by strings and each hash has two parts: a key that identifies each element of the hash and a value which is the data associated with the key. The name of a hash structure begins with the character %. In order to assign a hash key, we’ll write it like in the following code line: Here we have a short example of a hash structure called %NotebooksPrice: You can combine the three Perl data types enumerated above to get more complex data structures (like array of arrays, array of hashes, and so on). We tried above to enumerate some of the most important aspects of Perl data types, if you need more details, please check on CPAN or our link: Don't forget to check my new How To Tutorial eBooks (PDF format):
to see a lot of fully commented examples that help you use the Perl built-in functions and the Perl statements in your scripts. NEW!!! Do you want more information about the basic Perl topics? Check my new "Perl How To" Tutorial eBooks page where I'll answer the most frequent questions regarding some topics : Table of Contents: A Perl Script Install Perl Running Perl Perl Data Types Perl Variables Perl Operators Perl Lists Perl Arrays Array Size Array Length Perl Hashes Perl Statements Perl if Perl unless Perl switch Perl while Perl do-while Perl until Perl do-until Perl for Perl foreach Built-in Perl Functions Functions by Category String Functions List Functions Array Functions Hash Functions Miscellaneous Functions Functions in alphabetical order chomp chop chr crypt defined delete each grep hex index join lc lcfirst length map oct ord pack pop push q qw reverse rindex scalar shift sort splice split sprintf substr tr uc ucfirst undef unshift return from Perl Data Types to Perl Basics Hit the Alarm Clock!  |