autouse(3p) Perl Programmers Reference Guide autouse(3p) #

autouse(3p) Perl Programmers Reference Guide autouse(3p)

NNAAMMEE #

 autouse - postpone load of modules until a function is used

SSYYNNOOPPSSIISS #

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

DDEESSCCRRIIPPTTIIOONN #

 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 ffuunncc22(()) with prototype "($;$)", and ffuunncc11(()) 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 ffuunncc11(()) and ffuunncc22(()) in the current package.  When
 these functions are called, they load the package "Module" if needed, and
 substitute themselves with the correct definitions.

WWAARRNNIINNGG #

 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.

AAUUTTHHOORR #

 Ilya Zakharevich (ilya@math.ohio-state.edu)

SSEEEE AALLSSOO #

 ppeerrll(1).

perl v5.36.3 2017-02-05 autouse(3p)