# autouse - phpMan

## NAME
    autouse - postpone load of modules until a function is used

## SYNOPSIS
      use autouse 'Carp' => qw(carp croak);
      carp "this carp was predeclared and autoused ";

## DESCRIPTION
    If the module "Module" is already loaded, then the declaration

      use autouse 'Module' => qw(func1 func2($;$));

    is equivalent to

      use Module qw(func1 func2);

    if "Module" defines func2() with prototype "($;$)", and func1() has no
    prototypes. (At least if "Module" uses "Exporter"'s "import", otherwise
    it is a fatal error.)

    If the module "Module" is not loaded yet, then the above declaration
    declares functions func1() and func2() in the current package. When
    these functions are called, they load the package "Module" if needed,
    and substitute themselves with the correct definitions.

## WARNING
    Using "autouse" will move important steps of your program's execution
    from compile time to runtime. This can

    *   Break the execution of your program if the module you "autouse"d has
        some initialization which it expects to be done early.

    *   hide bugs in your code since important checks (like correctness of
        prototypes) is moved from compile time to runtime. In particular, if
        the prototype you specified on "autouse" line is wrong, you will not
        find it out until the corresponding function is executed. This will
        be very unfortunate for functions which are not always called (note
        that for such functions "autouse"ing gives biggest win, for a
        workaround see below).

    To alleviate the second problem (partially) it is advised to write your
    scripts like this:

      use Module;
      use autouse Module => qw(carp($) croak(&$));
      carp "this carp was predeclared and autoused ";

    The first line ensures that the errors in your argument specification
    are found early. When you ship your application you should comment out
    the first line, since it makes the second one useless.

## AUTHOR
    Ilya Zakharevich (<ilya@math.ohio-state.edu>)

## SEE ALSO
    [perl(1)].