perl/lib/AutoLoader.pm

package AutoLoader;

use strict;
use 5.006_001;

our($VERSION, $AUTOLOAD);

my $is_dosish;
my $is_epoc;
my $is_vms;
my $is_macos;

BEGIN {
    $is_dosish = $^O eq 'dos' || $^O eq 'os2' || $^O eq 'MSWin32' || $^O eq 'NetWare';
    $is_epoc = $^O eq 'epoc';
    $is_vms = $^O eq 'VMS';
    $is_macos = $^O eq 'MacOS';
    $VERSION = '5.60';
}

AUTOLOAD {
    my $sub = $AUTOLOAD;
    my $filename;
    # Braces used to preserve $1 et al.
    {
        # Try to find the autoloaded file from the package-qualified
        # name of the sub. e.g., if the sub needed is
        # Getopt::Long::GetOptions(), then $INC{Getopt/Long.pm} is
        # something like '/usr/lib/perl5/Getopt/Long.pm', and the
        # autoload file is '/usr/lib/perl5/auto/Getopt/Long/GetOptions.al'.
        #
        # However, if @INC is a relative path, this might not work.  If,
        # for example, @INC = ('lib'), then $INC{Getopt/Long.pm} is
        # 'lib/Getopt/Long.pm', and we want to require
        # 'auto/Getopt/Long/GetOptions.al' (without the leading 'lib').
        # In this case, we simple prepend the 'auto/' and let the
        # C<require> take care of the searching for us.

        my ($pkg,$func) = ($sub =~ /(.*)::([^:]+)$/);
        $pkg =~ s#::#/#g;
        if (defined($filename = $INC{"$pkg.pm"})) {
            if ($is_macos) {
                $pkg =~ tr#/#:#;
                $filename =~ s#^(.*)$pkg\.pm\z#$1auto:$pkg:$func.al#s;
            } else {
                $filename =~ s#^(.*)$pkg\.pm\z#$1auto/$pkg/$func.al#s;
            }

            # if the file exists, then make sure that it is a
            # a fully anchored path (i.e either '/usr/lib/auto/foo/bar.al',
            # or './lib/auto/foo/bar.al'.  This avoids C<require> searching
            # (and failing) to find the 'lib/auto/foo/bar.al' because it
            # looked for 'lib/lib/auto/foo/bar.al', given @INC = ('lib').

            if (-r $filename) {
                unless ($filename =~ m|^/|s) {
                    if ($is_dosish) {
                        unless ($filename =~ m{^([a-z]:)?[\\/]}is) {
                             if ($^O ne 'NetWare') {
                                        $filename = "./$filename";
                                } else {
                                        $filename = "$filename";
                                }
                        }
                    }
                    elsif ($is_epoc) {
                        unless ($filename =~ m{^([a-z?]:)?[\\/]}is) {
                             $filename = "./$filename";
                        }
                    }
                    elsif ($is_vms) {
                        # XXX todo by VMSmiths
                        $filename = "./$filename";
                    }
                    elsif (!$is_macos) {
                        $filename = "./$filename";
                    }
                }
            }
            else {
                $filename = undef;
            }
        }
        unless (defined $filename) {
            # let C<require> do the searching
            $filename = "auto/$sub.al";
            $filename =~ s#::#/#g;
        }
    }
    my $save = $@;
    local $!; # Do not munge the value. 
    eval { local $SIG{__DIE__}; require $filename };
    if ($@) {
        if (substr($sub,-9) eq '::DESTROY') {
            no strict 'refs';
            *$sub = sub {};
            $@ = undef;
        } elsif ($@ =~ /^Can't locate/) {
            # The load might just have failed because the filename was too
            # long for some old SVR3 systems which treat long names as errors.
            # If we can successfully truncate a long name then it's worth a go.
            # There is a slight risk that we could pick up the wrong file here
            # but autosplit should have warned about that when splitting.
            if ($filename =~ s/(\w{12,})\.al$/substr($1,0,11).".al"/e){
                eval { local $SIG{__DIE__}; require $filename };
            }
        }
        if ($@){
            $@ =~ s/ at .*\n//;
            my $error = $@;
            require Carp;
            Carp::croak($error);
        }
    }
    $@ = $save;
    goto &$sub;
}

sub import {
    my $pkg = shift;
    my $callpkg = caller;

    #
    # Export symbols, but not by accident of inheritance.
    #

    if ($pkg eq 'AutoLoader') {
        no strict 'refs';
        *{ $callpkg . '::AUTOLOAD' } = \&AUTOLOAD
            if @_ and $_[0] =~ /^&?AUTOLOAD$/;
    }

    #
    # Try to find the autosplit index file.  Eg., if the call package
    # is POSIX, then $INC{POSIX.pm} is something like
    # '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in
    # '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that.
    #
    # However, if @INC is a relative path, this might not work.  If,
    # for example, @INC = ('lib'), then
    # $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require
    # 'auto/POSIX/autosplit.ix' (without the leading 'lib').
    #

    (my $calldir = $callpkg) =~ s#::#/#g;
    my $path = $INC{$calldir . '.pm'};
    if (defined($path)) {
        # Try absolute path name.
        if ($is_macos) {
            (my $malldir = $calldir) =~ tr#/#:#;
            $path =~ s#^(.*)$malldir\.pm\z#$1auto:$malldir:autosplit.ix#s;
        } else {
            $path =~ s#^(.*)$calldir\.pm\z#$1auto/$calldir/autosplit.ix#;
        }

        eval { require $path; };
        # If that failed, try relative path with normal @INC searching.
        if ($@) {
            $path ="auto/$calldir/autosplit.ix";
            eval { require $path; };
        }
        if ($@) {
            my $error = $@;
            require Carp;
            Carp::carp($error);
        }
    } 
}

sub unimport {
    my $callpkg = caller;

    no strict 'refs';
    my $symname = $callpkg . '::AUTOLOAD';
    undef *{ $symname } if \&{ $symname } == \&AUTOLOAD;
    *{ $symname } = \&{ $symname };
}

1;

__END__

=head1 NAME

AutoLoader - load subroutines only on demand

=head1 SYNOPSIS

    package Foo;
    use AutoLoader 'AUTOLOAD';   # import the default AUTOLOAD subroutine

    package Bar;
    use AutoLoader;              # don't import AUTOLOAD, define our own
    sub AUTOLOAD {
        ...
        $AutoLoader::AUTOLOAD = "...";
        goto &AutoLoader::AUTOLOAD;
    }

=head1 DESCRIPTION

The B<AutoLoader> module works with the B<AutoSplit> module and the
C<__END__> token to defer the loading of some subroutines until they are
used rather than loading them all at once.

To use B<AutoLoader>, the author of a module has to place the
definitions of subroutines to be autoloaded after an C<__END__> token.
(See L<perldata>.)  The B<AutoSplit> module can then be run manually to
extract the definitions into individual files F<auto/funcname.al>.

B<AutoLoader> implements an AUTOLOAD subroutine.  When an undefined
subroutine in is called in a client module of B<AutoLoader>,
B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a
file with a name related to the location of the file from which the
client module was read.  As an example, if F<POSIX.pm> is located in
F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl
subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where
the C<.al> file has the same name as the subroutine, sans package.  If
such a file exists, AUTOLOAD will read and evaluate it,
thus (presumably) defining the needed subroutine.  AUTOLOAD will then
C<goto> the newly defined subroutine.

Once this process completes for a given function, it is defined, so
future calls to the subroutine will bypass the AUTOLOAD mechanism.

=head2 Subroutine Stubs

In order for object method lookup and/or prototype checking to operate
correctly even when methods have not yet been defined it is necessary to
"forward declare" each subroutine (as in C<sub NAME;>).  See
L<perlsub/"SYNOPSIS">.  Such forward declaration creates "subroutine
stubs", which are place holders with no code.

The AutoSplit and B<AutoLoader> modules automate the creation of forward
declarations.  The AutoSplit module creates an 'index' file containing
forward declarations of all the AutoSplit subroutines.  When the
AutoLoader module is 'use'd it loads these declarations into its callers
package.

Because of this mechanism it is important that B<AutoLoader> is always
C<use>d and not C<require>d.

=head2 Using B<AutoLoader>'s AUTOLOAD Subroutine

In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must>
explicitly import it:

    use AutoLoader 'AUTOLOAD';

=head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine

Some modules, mainly extensions, provide their own AUTOLOAD subroutines.
They typically need to check for some special cases (such as constants)
and then fallback to B<AutoLoader>'s AUTOLOAD for the rest.

Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine.
Instead, they should define their own AUTOLOAD subroutines along these
lines:

    use AutoLoader;
    use Carp;

    sub AUTOLOAD {
        my $sub = $AUTOLOAD;
        (my $constname = $sub) =~ s/.*:://;
        my $val = constant($constname, @_ ? $_[0] : 0);
        if ($! != 0) {
            if ($! =~ /Invalid/ || $!{EINVAL}) {
                $AutoLoader::AUTOLOAD = $sub;
                goto &AutoLoader::AUTOLOAD;
            }
            else {
                croak "Your vendor has not defined constant $constname";
            }
        }
        *$sub = sub { $val }; # same as: eval "sub $sub { $val }";
        goto &$sub;
    }

If any module's own AUTOLOAD subroutine has no need to fallback to the
AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit
subroutines), then that module should not use B<AutoLoader> at all.

=head2 Package Lexicals

Package lexicals declared with C<my> in the main block of a package
using B<AutoLoader> will not be visible to auto-loaded subroutines, due to
the fact that the given scope ends at the C<__END__> marker.  A module
using such variables as package globals will not work properly under the
B<AutoLoader>.

The C<vars> pragma (see L<perlmod/"vars">) may be used in such
situations as an alternative to explicitly qualifying all globals with
the package namespace.  Variables pre-declared with this pragma will be
visible to any autoloaded routines (but will not be invisible outside
the package, unfortunately).

=head2 Not Using AutoLoader

You can stop using AutoLoader by simply

        no AutoLoader;

=head2 B<AutoLoader> vs. B<SelfLoader>

The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the
loading of subroutines.

B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>.
While this avoids the use of a hierarchy of disk files and the
associated open/close for each routine loaded, B<SelfLoader> suffers a
startup speed disadvantage in the one-time parsing of the lines after
C<__DATA__>, after which routines are cached.  B<SelfLoader> can also
handle multiple packages in a file.

B<AutoLoader> only reads code as it is requested, and in many cases
should be faster, but requires a mechanism like B<AutoSplit> be used to
create the individual files.  L<ExtUtils::MakeMaker> will invoke
B<AutoSplit> automatically if B<AutoLoader> is used in a module source
file.

=head1 CAVEATS

AutoLoaders prior to Perl 5.002 had a slightly different interface.  Any
old modules which use B<AutoLoader> should be changed to the new calling
style.  Typically this just means changing a require to a use, adding
the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader>
from C<@ISA>.

On systems with restrictions on file name length, the file corresponding
to a subroutine may have a shorter name that the routine itself.  This
can lead to conflicting file names.  The I<AutoSplit> package warns of
these potential conflicts when used to split a module.

AutoLoader may fail to find the autosplit files (or even find the wrong
ones) in cases where C<@INC> contains relative paths, B<and> the program
does C<chdir>.

=head1 SEE ALSO

L<SelfLoader> - an autoloader that doesn't use external files.

=cut
Revision:	1.1
Committed:	Thu Jun 30 14:27:07 2005 UTC (21 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	package AutoLoader;
2
3			use strict;
4			use 5.006_001;
5
6			our($VERSION, $AUTOLOAD);
7
8			my $is_dosish;
9			my $is_epoc;
10			my $is_vms;
11			my $is_macos;
12
13			BEGIN {
14			$is_dosish = $^O eq 'dos' \|\| $^O eq 'os2' \|\| $^O eq 'MSWin32' \|\| $^O eq 'NetWare';
15			$is_epoc = $^O eq 'epoc';
16			$is_vms = $^O eq 'VMS';
17			$is_macos = $^O eq 'MacOS';
18			$VERSION = '5.60';
19			}
20
21			AUTOLOAD {
22			my $sub = $AUTOLOAD;
23			my $filename;
24			# Braces used to preserve $1 et al.
25			{
26			# Try to find the autoloaded file from the package-qualified
27			# name of the sub. e.g., if the sub needed is
28			# Getopt::Long::GetOptions(), then $INC{Getopt/Long.pm} is
29			# something like '/usr/lib/perl5/Getopt/Long.pm', and the
30			# autoload file is '/usr/lib/perl5/auto/Getopt/Long/GetOptions.al'.
31			#
32			# However, if @INC is a relative path, this might not work. If,
33			# for example, @INC = ('lib'), then $INC{Getopt/Long.pm} is
34			# 'lib/Getopt/Long.pm', and we want to require
35			# 'auto/Getopt/Long/GetOptions.al' (without the leading 'lib').
36			# In this case, we simple prepend the 'auto/' and let the
37			# C<require> take care of the searching for us.
38
39			my ($pkg,$func) = ($sub =~ /(.*)::([^:]+)$/);
40			$pkg =~ s#::#/#g;
41			if (defined($filename = $INC{"$pkg.pm"})) {
42			if ($is_macos) {
43			$pkg =~ tr#/#:#;
44			$filename =~ s#^(.*)$pkg\.pm\z#$1auto:$pkg:$func.al#s;
45			} else {
46			$filename =~ s#^(.*)$pkg\.pm\z#$1auto/$pkg/$func.al#s;
47			}
48
49			# if the file exists, then make sure that it is a
50			# a fully anchored path (i.e either '/usr/lib/auto/foo/bar.al',
51			# or './lib/auto/foo/bar.al'. This avoids C<require> searching
52			# (and failing) to find the 'lib/auto/foo/bar.al' because it
53			# looked for 'lib/lib/auto/foo/bar.al', given @INC = ('lib').
54
55			if (-r $filename) {
56			unless ($filename =~ m\|^/\|s) {
57			if ($is_dosish) {
58			unless ($filename =~ m{^([a-z]:)?[\\/]}is) {
59			if ($^O ne 'NetWare') {
60			$filename = "./$filename";
61			} else {
62			$filename = "$filename";
63			}
64			}
65			}
66			elsif ($is_epoc) {
67			unless ($filename =~ m{^([a-z?]:)?[\\/]}is) {
68			$filename = "./$filename";
69			}
70			}
71			elsif ($is_vms) {
72			# XXX todo by VMSmiths
73			$filename = "./$filename";
74			}
75			elsif (!$is_macos) {
76			$filename = "./$filename";
77			}
78			}
79			}
80			else {
81			$filename = undef;
82			}
83			}
84			unless (defined $filename) {
85			# let C<require> do the searching
86			$filename = "auto/$sub.al";
87			$filename =~ s#::#/#g;
88			}
89			}
90			my $save = $@;
91			local $!; # Do not munge the value.
92			eval { local $SIG{__DIE__}; require $filename };
93			if ($@) {
94			if (substr($sub,-9) eq '::DESTROY') {
95			no strict 'refs';
96			*$sub = sub {};
97			$@ = undef;
98			} elsif ($@ =~ /^Can't locate/) {
99			# The load might just have failed because the filename was too
100			# long for some old SVR3 systems which treat long names as errors.
101			# If we can successfully truncate a long name then it's worth a go.
102			# There is a slight risk that we could pick up the wrong file here
103			# but autosplit should have warned about that when splitting.
104			if ($filename =~ s/(\w{12,})\.al$/substr($1,0,11).".al"/e){
105			eval { local $SIG{__DIE__}; require $filename };
106			}
107			}
108			if ($@){
109			$@ =~ s/ at .*\n//;
110			my $error = $@;
111			require Carp;
112			Carp::croak($error);
113			}
114			}
115			$@ = $save;
116			goto &$sub;
117			}
118
119			sub import {
120			my $pkg = shift;
121			my $callpkg = caller;
122
123			#
124			# Export symbols, but not by accident of inheritance.
125			#
126
127			if ($pkg eq 'AutoLoader') {
128			no strict 'refs';
129			*{ $callpkg . '::AUTOLOAD' } = \&AUTOLOAD
130			if @_ and $_[0] =~ /^&?AUTOLOAD$/;
131			}
132
133			#
134			# Try to find the autosplit index file. Eg., if the call package
135			# is POSIX, then $INC{POSIX.pm} is something like
136			# '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in
137			# '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that.
138			#
139			# However, if @INC is a relative path, this might not work. If,
140			# for example, @INC = ('lib'), then
141			# $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require
142			# 'auto/POSIX/autosplit.ix' (without the leading 'lib').
143			#
144
145			(my $calldir = $callpkg) =~ s#::#/#g;
146			my $path = $INC{$calldir . '.pm'};
147			if (defined($path)) {
148			# Try absolute path name.
149			if ($is_macos) {
150			(my $malldir = $calldir) =~ tr#/#:#;
151			$path =~ s#^(.*)$malldir\.pm\z#$1auto:$malldir:autosplit.ix#s;
152			} else {
153			$path =~ s#^(.*)$calldir\.pm\z#$1auto/$calldir/autosplit.ix#;
154			}
155
156			eval { require $path; };
157			# If that failed, try relative path with normal @INC searching.
158			if ($@) {
159			$path ="auto/$calldir/autosplit.ix";
160			eval { require $path; };
161			}
162			if ($@) {
163			my $error = $@;
164			require Carp;
165			Carp::carp($error);
166			}
167			}
168			}
169
170			sub unimport {
171			my $callpkg = caller;
172
173			no strict 'refs';
174			my $symname = $callpkg . '::AUTOLOAD';
175			undef *{ $symname } if \&{ $symname } == \&AUTOLOAD;
176			*{ $symname } = \&{ $symname };
177			}
178
179			1;
180
181			__END__
182
183			=head1 NAME
184
185			AutoLoader - load subroutines only on demand
186
187			=head1 SYNOPSIS
188
189			package Foo;
190			use AutoLoader 'AUTOLOAD'; # import the default AUTOLOAD subroutine
191
192			package Bar;
193			use AutoLoader; # don't import AUTOLOAD, define our own
194			sub AUTOLOAD {
195			...
196			$AutoLoader::AUTOLOAD = "...";
197			goto &AutoLoader::AUTOLOAD;
198			}
199
200			=head1 DESCRIPTION
201
202			The B<AutoLoader> module works with the B<AutoSplit> module and the
203			C<__END__> token to defer the loading of some subroutines until they are
204			used rather than loading them all at once.
205
206			To use B<AutoLoader>, the author of a module has to place the
207			definitions of subroutines to be autoloaded after an C<__END__> token.
208			(See L<perldata>.) The B<AutoSplit> module can then be run manually to
209			extract the definitions into individual files F<auto/funcname.al>.
210
211			B<AutoLoader> implements an AUTOLOAD subroutine. When an undefined
212			subroutine in is called in a client module of B<AutoLoader>,
213			B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a
214			file with a name related to the location of the file from which the
215			client module was read. As an example, if F<POSIX.pm> is located in
216			F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl
217			subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where
218			the C<.al> file has the same name as the subroutine, sans package. If
219			such a file exists, AUTOLOAD will read and evaluate it,
220			thus (presumably) defining the needed subroutine. AUTOLOAD will then
221			C<goto> the newly defined subroutine.
222
223			Once this process completes for a given function, it is defined, so
224			future calls to the subroutine will bypass the AUTOLOAD mechanism.
225
226			=head2 Subroutine Stubs
227
228			In order for object method lookup and/or prototype checking to operate
229			correctly even when methods have not yet been defined it is necessary to
230			"forward declare" each subroutine (as in C<sub NAME;>). See
231			L<perlsub/"SYNOPSIS">. Such forward declaration creates "subroutine
232			stubs", which are place holders with no code.
233
234			The AutoSplit and B<AutoLoader> modules automate the creation of forward
235			declarations. The AutoSplit module creates an 'index' file containing
236			forward declarations of all the AutoSplit subroutines. When the
237			AutoLoader module is 'use'd it loads these declarations into its callers
238			package.
239
240			Because of this mechanism it is important that B<AutoLoader> is always
241			C<use>d and not C<require>d.
242
243			=head2 Using B<AutoLoader>'s AUTOLOAD Subroutine
244
245			In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must>
246			explicitly import it:
247
248			use AutoLoader 'AUTOLOAD';
249
250			=head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine
251
252			Some modules, mainly extensions, provide their own AUTOLOAD subroutines.
253			They typically need to check for some special cases (such as constants)
254			and then fallback to B<AutoLoader>'s AUTOLOAD for the rest.
255
256			Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine.
257			Instead, they should define their own AUTOLOAD subroutines along these
258			lines:
259
260			use AutoLoader;
261			use Carp;
262
263			sub AUTOLOAD {
264			my $sub = $AUTOLOAD;
265			(my $constname = $sub) =~ s/.*:://;
266			my $val = constant($constname, @_ ? $_[0] : 0);
267			if ($! != 0) {
268			if ($! =~ /Invalid/ \|\| $!{EINVAL}) {
269			$AutoLoader::AUTOLOAD = $sub;
270			goto &AutoLoader::AUTOLOAD;
271			}
272			else {
273			croak "Your vendor has not defined constant $constname";
274			}
275			}
276			*$sub = sub { $val }; # same as: eval "sub $sub { $val }";
277			goto &$sub;
278			}
279
280			If any module's own AUTOLOAD subroutine has no need to fallback to the
281			AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit
282			subroutines), then that module should not use B<AutoLoader> at all.
283
284			=head2 Package Lexicals
285
286			Package lexicals declared with C<my> in the main block of a package
287			using B<AutoLoader> will not be visible to auto-loaded subroutines, due to
288			the fact that the given scope ends at the C<__END__> marker. A module
289			using such variables as package globals will not work properly under the
290			B<AutoLoader>.
291
292			The C<vars> pragma (see L<perlmod/"vars">) may be used in such
293			situations as an alternative to explicitly qualifying all globals with
294			the package namespace. Variables pre-declared with this pragma will be
295			visible to any autoloaded routines (but will not be invisible outside
296			the package, unfortunately).
297
298			=head2 Not Using AutoLoader
299
300			You can stop using AutoLoader by simply
301
302			no AutoLoader;
303
304			=head2 B<AutoLoader> vs. B<SelfLoader>
305
306			The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the
307			loading of subroutines.
308
309			B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>.
310			While this avoids the use of a hierarchy of disk files and the
311			associated open/close for each routine loaded, B<SelfLoader> suffers a
312			startup speed disadvantage in the one-time parsing of the lines after
313			C<__DATA__>, after which routines are cached. B<SelfLoader> can also
314			handle multiple packages in a file.
315
316			B<AutoLoader> only reads code as it is requested, and in many cases
317			should be faster, but requires a mechanism like B<AutoSplit> be used to
318			create the individual files. L<ExtUtils::MakeMaker> will invoke
319			B<AutoSplit> automatically if B<AutoLoader> is used in a module source
320			file.
321
322			=head1 CAVEATS
323
324			AutoLoaders prior to Perl 5.002 had a slightly different interface. Any
325			old modules which use B<AutoLoader> should be changed to the new calling
326			style. Typically this just means changing a require to a use, adding
327			the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader>
328			from C<@ISA>.
329
330			On systems with restrictions on file name length, the file corresponding
331			to a subroutine may have a shorter name that the routine itself. This
332			can lead to conflicting file names. The I<AutoSplit> package warns of
333			these potential conflicts when used to split a module.
334
335			AutoLoader may fail to find the autosplit files (or even find the wrong
336			ones) in cases where C<@INC> contains relative paths, B<and> the program
337			does C<chdir>.
338
339			=head1 SEE ALSO
340
341			L<SelfLoader> - an autoloader that doesn't use external files.
342
343			=cut