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autouse (3)
  • >> autouse (3) ( Solaris man: Библиотечные вызовы )
  • autouse (3) ( Linux man: Библиотечные вызовы )
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    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($;$) Module::func3);
    
         is equivalent to
    
           use Module qw(func1 func2);
    
         if `Module' defines func2() with prototype `($;$)', and
         func1() and func3() have 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, and declares a function Module::func3().
         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
    
         o   Break the execution of your program if the module you
             `autouse'd has some initialization which it expects to
             be done early.
    
         o   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).
    
    
    
    


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