Built-in Perl FunctionsNEW!!! Check my new resource: Perl How To Tutorial eBooks It’s beyond the scope of this section to clear all the aspects related to functions in a programming language. In general, a function has a name and represents a block of code which we can call anywhere we need in a program source. We use the functions in order not to repeat indefinitely the same block of code using the copy and paste techniques. A function can have 1, 2, 3 or more parameters or even none. A parameter is a value passed to a function and could be a scalar, a list, a reference or whatever. In general, in order to call a function, we write first the name of the function, followed by parentheses. The calling parameters are separated by commas and are included inside the parentheses. In Perl we can call a function either by using parentheses or without them. The calling of a function has as result a value which is returned by that respective function. We’ll give you as example the push() function which has the syntax: where push is the name of the function, and @array and list are the arguments of the function. This function adds a list of values at the end of an array and returns the new number of the elements of the array in the scalar variable $newNumber. In Perl we can use a function as a term in an expression. When Perl meets the name of a function in a Perl script, it stops executing the sequential lines of code and continues with the execution of the function code. After finishing the execution of the function, Perl returns back at the point from where the function was called, and continues with the current code that follows the called function. Besides the built-in Perl functions, there are a lot of other functions available in the myriad of Perl modules available through CPAN. In order to use these functions, first you must declare through the clause "use" the module you intend to use. And last but not least you must search through the module documentation to see what functions are available and how to use them. We’ll hence describe only the most relevant built-in Perl functions, which are used more frequently in Perl scripts. The built-in Perl functions are grouped in the following categories:
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 Array Functions Functions in alphabetical order chomp chop chr crypt defined grep hex index join lc lcfirst length map oct ord pack pop push qw reverse rindex scalar shift splice split substr uc undef unshift return to Perl Basics Hit the Alarm Clock! 
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