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Invoking Functions

Use postfix ( Fixity) parentheses to invoke a named function. Any arguments to the function may go within the parentheses:

Function Parameters

A function receives its parameters in a single array, @_ ( The Default Array Variables ). When you invoke a function, Perl flattens all provided arguments into a single list. The function must either unpack its parameters into variables or operate on @_ directly:

Functions and Namespaces

Every function has a containing namespace ( Packages ). Functions in an undeclared namespace—functions not declared within the scope of an explicit package statement—exist in the main namespace. You may also declare a function within another namespace by prefixing its name:

Reporting Errors

Use the caller builtin to inspect a function's calling context. When passed no arguments, caller returns a list containing the name of the calling package, the name of the file containing the call, and the line number of the file on which the call occurred:

Pitfalls and Misfeatures

Perl still supports old-style invocations of functions, carried over from ancient versions of Perl. Previous versions of Perl required you to invoke functions with a leading ampersand ( &) character:

Scope

Everything with a name in Perl (a variable, a function, a filehandle, a class) has a scope. This scope governs the lifespan and visibility of these entities. Scoping helps to enforce encapsulation —keeping related concepts together and preventing their details from leaking.

Anonymous Functions

An anonymous function is a function without a name. It behaves exactly like a named function—you can invoke it, pass it arguments, return values from it, and take references to it. Yet you can only access an anonymous function by reference ( Function References ), not by name.