Sams Teach Yourself Perl in 24 Hours

Hour 8. Functions

Almost all computer languages support functions. A function is a group of code that can be called by name to do some work and then return some value. You've been using functions throughout this book; for example, you've used print, reverse, sort, open, close, split, and so on. They are Perl's built-in functions.

Perl also allows you to write your own functions. In Perl, user-defined functions are called subroutines, or subs. Like Perl's built-in functions, user-defined functions can take arguments and return values to the caller.

Perl also supports the concept of scope. Scope determines the set of variables visible to the program at a given time. Because of Perl's scope, you can write functions that can behave autonomously ...