debian man page for aspect::advice::before

Aspect::Advice::Before(3pm)				User Contributed Perl Documentation			       Aspect::Advice::Before(3pm)

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 . "
";

	     # 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 Adam Kennedy.

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

perl v5.14.2							    2012-02-01					       Aspect::Advice::Before(3pm)