---
name: "Aspect::Advice::Before"
section: "3pm"
platform: "linux"
package: "libaspect-perl"
version: "1.04-3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Aspect::Advice::Before"
---

# Aspect::Advice::Before(3pm)

Execute code before a function is called

## NAME

Aspect::Advice::Before - Execute code before a function is called

## SYNOPSIS

```
  use Aspect;

  before {

      # Trace all calls to your module
      print STDERR "Called my function " . $_->sub_name . "\n";

      # Shortcut calls to foo() to always be true
      if ( $_->short_name eq 'foo' ) {
          return $_->return_value(1);
      }

      # Add an extra flag to bar() but call as normal
      if ( $_->short_name eq 'bar' ) {
          $_->args( $_->args, 'flag' );
      }
  } call qr/^ MyModule::\w+ $/
```

## DESCRIPTION

The `"before"` advice type is used to execute advice code prior to entry into a target function. It is implemented by **Aspect::Advice::Before**.

As well as creating side effects that run before the main code, the `"before"` advice type is particularly useful for changing parameters or shortcutting calls to functions entirely and replacing the value they would normally return with a different value.

Please note that the `"highest"` pointcut (Aspect::Pointcut::Highest) is incompatible with `"before"`. Creating a `"before"` advice with a pointcut tree that contains a `"highest"` pointcut will result in an exception.

If speed is important to your program then `"before"` is particular interesting as the `"before"` implementation is the only one that can take advantage of tail calls via Perl's `"goto"` function, where the rest of the advice types need the more costly Sub::Uplevel to keep **caller()** returning correctly.

## AUTHORS

Adam Kennedy \<adamk@cpan.org\>

## COPYRIGHT AND LICENSE

Copyright 2010 - 2013 Adam Kennedy.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.