#use strict; # debugging only
use 5.003_90
; # ->can, for my $var
$autouse::VERSION
= '1.03';
my $class = @_ ?
shift : 'autouse';
croak
"usage: use $class MODULE [,SUBS...]" unless @_;
(my $pm = $module) =~ s{::}{/}g;
local $Exporter::ExportLevel
= $Exporter::ExportLevel
+ 1;
# $Exporter::Verbose = 1;
return $module->import(map { (my $f = $_) =~ s/\(.*?\)$//; $f } @_);
# It is not loaded: need to do real work.
print "autouse called from $callpkg\n" if $autouse::DEBUG
;
$proto = $1 if (my $func = $f) =~ s/\((.*)\)$//;
my $closure_import_func = $func; # Full name
my $closure_func = $func; # Name inside package
my $index = rindex($func, '::');
$closure_import_func = "${callpkg}::$func";
$closure_func = substr $func, $index + 2;
croak
"autouse into different package attempted"
unless substr($func, 0, $index) eq $module;
*$closure_import_func = \
&{"${module}::$closure_func"};
print "autousing $module; "
."imported $closure_func as $closure_import_func\n"
goto &$closure_import_func;
*$closure_import_func = eval "sub ($proto) { &\$load_sub }";
*$closure_import_func = $load_sub;
if (my $import = $module->can('import')) {
croak
"autoused module has unique import() method"
unless defined(&Exporter
::import
)
&& $import == \
&Exporter
::import
;
autouse - postpone load of modules until a function is used
use autouse 'Carp' => qw(carp croak);
carp "this carp was predeclared and autoused ";
If the module C<Module> is already loaded, then the declaration
use autouse 'Module' => qw(func1 func2($;$));
use Module qw(func1 func2);
if C<Module> defines func2() with prototype C<($;$)>, and func1() has
no prototypes. (At least if C<Module> uses C<Exporter>'s C<import>,
otherwise it is a fatal error.)
If the module C<Module> is not loaded yet, then the above declaration
declares functions func1() and func2() in the current package. When
these functions are called, they load the package C<Module> if needed,
and substitute themselves with the correct definitions.
use Module qw(Module::func3);
will work and is the equivalent to:
It is not a very useful feature and has been deprecated.
Using C<autouse> will move important steps of your program's execution
from compile time to runtime. This can
Break the execution of your program if the module you C<autouse>d has
some initialization which it expects to be done early.
hide bugs in your code since important checks (like correctness of
prototypes) is moved from compile time to runtime. In particular, if
the prototype you specified on C<autouse> line is wrong, you will not
find it out until the corresponding function is executed. This will be
very unfortunate for functions which are not always called (note that
for such functions C<autouse>ing gives biggest win, for a workaround
To alleviate the second problem (partially) it is advised to write
use autouse Module => qw(carp($) 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.
Ilya Zakharevich (ilya@math.ohio-state.edu)