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1 | package SelfLoader; |
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2 | # use Carp; |
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3 | require Exporter; |
4 | @ISA = qw(Exporter); |
5 | @EXPORT = qw(AUTOLOAD); |
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6 | $VERSION = "1.0904"; |
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7 | sub Version {$VERSION} |
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8 | $DEBUG = 0; |
9 | |
10 | my %Cache; # private cache for all SelfLoader's client packages |
11 | |
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12 | # allow checking for valid ': attrlist' attachments |
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13 | # (we use 'our' rather than 'my' here, due to the rather complex and buggy |
14 | # behaviour of lexicals with qr// and (??{$lex}) ) |
15 | our $nested; |
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16 | $nested = qr{ \( (?: (?> [^()]+ ) | (??{ $nested }) )* \) }x; |
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17 | our $one_attr = qr{ (?> (?! \d) \w+ (?:$nested)? ) (?:\s*\:\s*|\s+(?!\:)) }x; |
18 | our $attr_list = qr{ \s* : \s* (?: $one_attr )* }x; |
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19 | |
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20 | sub croak { require Carp; goto &Carp::croak } |
21 | |
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22 | AUTOLOAD { |
23 | print STDERR "SelfLoader::AUTOLOAD for $AUTOLOAD\n" if $DEBUG; |
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24 | my $SL_code = $Cache{$AUTOLOAD}; |
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25 | my $save = $@; # evals in both AUTOLOAD and _load_stubs can corrupt $@ |
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26 | unless ($SL_code) { |
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27 | # Maybe this pack had stubs before __DATA__, and never initialized. |
28 | # Or, this maybe an automatic DESTROY method call when none exists. |
29 | $AUTOLOAD =~ m/^(.*)::/; |
30 | SelfLoader->_load_stubs($1) unless exists $Cache{"${1}::<DATA"}; |
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31 | $SL_code = $Cache{$AUTOLOAD}; |
32 | $SL_code = "sub $AUTOLOAD { }" |
33 | if (!$SL_code and $AUTOLOAD =~ m/::DESTROY$/); |
34 | croak "Undefined subroutine $AUTOLOAD" unless $SL_code; |
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35 | } |
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36 | print STDERR "SelfLoader::AUTOLOAD eval: $SL_code\n" if $DEBUG; |
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37 | |
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38 | eval $SL_code; |
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39 | if ($@) { |
40 | $@ =~ s/ at .*\n//; |
41 | croak $@; |
42 | } |
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43 | $@ = $save; |
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44 | defined(&$AUTOLOAD) || die "SelfLoader inconsistency error"; |
45 | delete $Cache{$AUTOLOAD}; |
46 | goto &$AUTOLOAD |
47 | } |
48 | |
49 | sub load_stubs { shift->_load_stubs((caller)[0]) } |
50 | |
51 | sub _load_stubs { |
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52 | # $endlines is used by Devel::SelfStubber to capture lines after __END__ |
53 | my($self, $callpack, $endlines) = @_; |
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54 | my $fh = \*{"${callpack}::DATA"}; |
55 | my $currpack = $callpack; |
56 | my($line,$name,@lines, @stubs, $protoype); |
57 | |
58 | print STDERR "SelfLoader::load_stubs($callpack)\n" if $DEBUG; |
59 | croak("$callpack doesn't contain an __DATA__ token") |
60 | unless fileno($fh); |
61 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached |
62 | |
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63 | local($/) = "\n"; |
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64 | while(defined($line = <$fh>) and $line !~ m/^__END__/) { |
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65 | if ($line =~ m/^sub\s+([\w:]+)\s*((?:\([\\\$\@\%\&\*\;]*\))?(?:$attr_list)?)/) { |
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66 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
67 | $protoype = $2; |
68 | @lines = ($line); |
69 | if (index($1,'::') == -1) { # simple sub name |
70 | $name = "${currpack}::$1"; |
71 | } else { # sub name with package |
72 | $name = $1; |
73 | $name =~ m/^(.*)::/; |
74 | if (defined(&{"${1}::AUTOLOAD"})) { |
75 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || |
76 | die 'SelfLoader Error: attempt to specify Selfloading', |
77 | " sub $name in non-selfloading module $1"; |
78 | } else { |
79 | $self->export($1,'AUTOLOAD'); |
80 | } |
81 | } |
82 | } elsif ($line =~ m/^package\s+([\w:]+)/) { # A package declared |
83 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
84 | $self->_package_defined($line); |
85 | $name = ''; |
86 | @lines = (); |
87 | $currpack = $1; |
88 | $Cache{"${currpack}::<DATA"} = 1; # indicate package is cached |
89 | if (defined(&{"${1}::AUTOLOAD"})) { |
90 | \&{"${1}::AUTOLOAD"} == \&SelfLoader::AUTOLOAD || |
91 | die 'SelfLoader Error: attempt to specify Selfloading', |
92 | " package $currpack which already has AUTOLOAD"; |
93 | } else { |
94 | $self->export($currpack,'AUTOLOAD'); |
95 | } |
96 | } else { |
97 | push(@lines,$line); |
98 | } |
99 | } |
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100 | if (defined($line) && $line =~ /^__END__/) { # __END__ |
101 | unless ($line =~ /^__END__\s*DATA/) { |
102 | if ($endlines) { |
103 | # Devel::SelfStubber would like us to capture the lines after |
104 | # __END__ so it can write out the entire file |
105 | @$endlines = <$fh>; |
106 | } |
107 | close($fh); |
108 | } |
109 | } |
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110 | push(@stubs, $self->_add_to_cache($name, $currpack, \@lines, $protoype)); |
111 | eval join('', @stubs) if @stubs; |
112 | } |
113 | |
114 | |
115 | sub _add_to_cache { |
116 | my($self,$fullname,$pack,$lines, $protoype) = @_; |
117 | return () unless $fullname; |
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118 | (require Carp), Carp::carp("Redefining sub $fullname") |
119 | if exists $Cache{$fullname}; |
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120 | $Cache{$fullname} = join('', "package $pack; ",@$lines); |
121 | print STDERR "SelfLoader cached $fullname: $Cache{$fullname}" if $DEBUG; |
122 | # return stub to be eval'd |
123 | defined($protoype) ? "sub $fullname $protoype;" : "sub $fullname;" |
124 | } |
125 | |
126 | sub _package_defined {} |
127 | |
128 | 1; |
129 | __END__ |
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130 | |
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131 | =head1 NAME |
132 | |
133 | SelfLoader - load functions only on demand |
134 | |
135 | =head1 SYNOPSIS |
136 | |
137 | package FOOBAR; |
138 | use SelfLoader; |
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139 | |
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140 | ... (initializing code) |
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141 | |
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142 | __DATA__ |
143 | sub {.... |
144 | |
145 | |
146 | =head1 DESCRIPTION |
147 | |
148 | This module tells its users that functions in the FOOBAR package are to be |
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149 | autoloaded from after the C<__DATA__> token. See also |
150 | L<perlsub/"Autoloading">. |
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151 | |
152 | =head2 The __DATA__ token |
153 | |
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154 | The C<__DATA__> token tells the perl compiler that the perl code |
155 | for compilation is finished. Everything after the C<__DATA__> token |
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156 | is available for reading via the filehandle FOOBAR::DATA, |
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157 | where FOOBAR is the name of the current package when the C<__DATA__> |
158 | token is reached. This works just the same as C<__END__> does in |
159 | package 'main', but for other modules data after C<__END__> is not |
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160 | automatically retrievable, whereas data after C<__DATA__> is. |
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161 | The C<__DATA__> token is not recognized in versions of perl prior to |
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162 | 5.001m. |
163 | |
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164 | Note that it is possible to have C<__DATA__> tokens in the same package |
165 | in multiple files, and that the last C<__DATA__> token in a given |
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166 | package that is encountered by the compiler is the one accessible |
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167 | by the filehandle. This also applies to C<__END__> and main, i.e. if |
168 | the 'main' program has an C<__END__>, but a module 'require'd (_not_ 'use'd) |
169 | by that program has a 'package main;' declaration followed by an 'C<__DATA__>', |
170 | then the C<DATA> filehandle is set to access the data after the C<__DATA__> |
171 | in the module, _not_ the data after the C<__END__> token in the 'main' |
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172 | program, since the compiler encounters the 'require'd file later. |
173 | |
174 | =head2 SelfLoader autoloading |
175 | |
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176 | The B<SelfLoader> works by the user placing the C<__DATA__> |
177 | token I<after> perl code which needs to be compiled and |
178 | run at 'require' time, but I<before> subroutine declarations |
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179 | that can be loaded in later - usually because they may never |
180 | be called. |
181 | |
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182 | The B<SelfLoader> will read from the FOOBAR::DATA filehandle to |
183 | load in the data after C<__DATA__>, and load in any subroutine |
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184 | when it is called. The costs are the one-time parsing of the |
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185 | data after C<__DATA__>, and a load delay for the _first_ |
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186 | call of any autoloaded function. The benefits (hopefully) |
187 | are a speeded up compilation phase, with no need to load |
188 | functions which are never used. |
189 | |
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190 | The B<SelfLoader> will stop reading from C<__DATA__> if |
191 | it encounters the C<__END__> token - just as you would expect. |
192 | If the C<__END__> token is present, and is followed by the |
193 | token DATA, then the B<SelfLoader> leaves the FOOBAR::DATA |
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194 | filehandle open on the line after that token. |
195 | |
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196 | The B<SelfLoader> exports the C<AUTOLOAD> subroutine to the |
197 | package using the B<SelfLoader>, and this loads the called |
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198 | subroutine when it is first called. |
199 | |
200 | There is no advantage to putting subroutines which will _always_ |
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201 | be called after the C<__DATA__> token. |
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202 | |
203 | =head2 Autoloading and package lexicals |
204 | |
205 | A 'my $pack_lexical' statement makes the variable $pack_lexical |
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206 | local _only_ to the file up to the C<__DATA__> token. Subroutines |
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207 | declared elsewhere _cannot_ see these types of variables, |
208 | just as if you declared subroutines in the package but in another |
209 | file, they cannot see these variables. |
210 | |
211 | So specifically, autoloaded functions cannot see package |
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212 | lexicals (this applies to both the B<SelfLoader> and the Autoloader). |
213 | The C<vars> pragma provides an alternative to defining package-level |
214 | globals that will be visible to autoloaded routines. See the documentation |
215 | on B<vars> in the pragma section of L<perlmod>. |
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216 | |
217 | =head2 SelfLoader and AutoLoader |
218 | |
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219 | The B<SelfLoader> can replace the AutoLoader - just change 'use AutoLoader' |
220 | to 'use SelfLoader' (though note that the B<SelfLoader> exports |
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221 | the AUTOLOAD function - but if you have your own AUTOLOAD and |
222 | are using the AutoLoader too, you probably know what you're doing), |
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223 | and the C<__END__> token to C<__DATA__>. You will need perl version 5.001m |
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224 | or later to use this (version 5.001 with all patches up to patch m). |
225 | |
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226 | There is no need to inherit from the B<SelfLoader>. |
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227 | |
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228 | The B<SelfLoader> works similarly to the AutoLoader, but picks up the |
229 | subs from after the C<__DATA__> instead of in the 'lib/auto' directory. |
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230 | There is a maintenance gain in not needing to run AutoSplit on the module |
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231 | at installation, and a runtime gain in not needing to keep opening and |
232 | closing files to load subs. There is a runtime loss in needing |
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233 | to parse the code after the C<__DATA__>. Details of the B<AutoLoader> and |
234 | another view of these distinctions can be found in that module's |
235 | documentation. |
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236 | |
237 | =head2 __DATA__, __END__, and the FOOBAR::DATA filehandle. |
238 | |
239 | This section is only relevant if you want to use |
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240 | the C<FOOBAR::DATA> together with the B<SelfLoader>. |
241 | |
242 | Data after the C<__DATA__> token in a module is read using the |
243 | FOOBAR::DATA filehandle. C<__END__> can still be used to denote the end |
244 | of the C<__DATA__> section if followed by the token DATA - this is supported |
245 | by the B<SelfLoader>. The C<FOOBAR::DATA> filehandle is left open if an |
246 | C<__END__> followed by a DATA is found, with the filehandle positioned at |
247 | the start of the line after the C<__END__> token. If no C<__END__> token is |
248 | present, or an C<__END__> token with no DATA token on the same line, then |
249 | the filehandle is closed. |
250 | |
251 | The B<SelfLoader> reads from wherever the current |
252 | position of the C<FOOBAR::DATA> filehandle is, until the |
253 | EOF or C<__END__>. This means that if you want to use |
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254 | that filehandle (and ONLY if you want to), you should either |
255 | |
256 | 1. Put all your subroutine declarations immediately after |
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257 | the C<__DATA__> token and put your own data after those |
258 | declarations, using the C<__END__> token to mark the end |
259 | of subroutine declarations. You must also ensure that the B<SelfLoader> |
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260 | reads first by calling 'SelfLoader-E<gt>load_stubs();', or by using a |
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261 | function which is selfloaded; |
262 | |
263 | or |
264 | |
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265 | 2. You should read the C<FOOBAR::DATA> filehandle first, leaving |
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266 | the handle open and positioned at the first line of subroutine |
267 | declarations. |
268 | |
269 | You could conceivably do both. |
270 | |
271 | =head2 Classes and inherited methods. |
272 | |
273 | For modules which are not classes, this section is not relevant. |
274 | This section is only relevant if you have methods which could |
275 | be inherited. |
276 | |
277 | A subroutine stub (or forward declaration) looks like |
278 | |
279 | sub stub; |
280 | |
281 | i.e. it is a subroutine declaration without the body of the |
282 | subroutine. For modules which are not classes, there is no real |
283 | need for stubs as far as autoloading is concerned. |
284 | |
285 | For modules which ARE classes, and need to handle inherited methods, |
286 | stubs are needed to ensure that the method inheritance mechanism works |
287 | properly. You can load the stubs into the module at 'require' time, by |
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288 | adding the statement 'SelfLoader-E<gt>load_stubs();' to the module to do |
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289 | this. |
290 | |
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291 | The alternative is to put the stubs in before the C<__DATA__> token BEFORE |
292 | releasing the module, and for this purpose the C<Devel::SelfStubber> |
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293 | module is available. However this does require the extra step of ensuring |
294 | that the stubs are in the module. If this is done I strongly recommend |
295 | that this is done BEFORE releasing the module - it should NOT be done |
296 | at install time in general. |
297 | |
298 | =head1 Multiple packages and fully qualified subroutine names |
299 | |
300 | Subroutines in multiple packages within the same file are supported - but you |
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301 | should note that this requires exporting the C<SelfLoader::AUTOLOAD> to |
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302 | every package which requires it. This is done automatically by the |
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303 | B<SelfLoader> when it first loads the subs into the cache, but you should |
304 | really specify it in the initialization before the C<__DATA__> by putting |
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305 | a 'use SelfLoader' statement in each package. |
306 | |
307 | Fully qualified subroutine names are also supported. For example, |
308 | |
309 | __DATA__ |
310 | sub foo::bar {23} |
311 | package baz; |
312 | sub dob {32} |
313 | |
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314 | will all be loaded correctly by the B<SelfLoader>, and the B<SelfLoader> |
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315 | will ensure that the packages 'foo' and 'baz' correctly have the |
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316 | B<SelfLoader> C<AUTOLOAD> method when the data after C<__DATA__> is first |
317 | parsed. |
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318 | |
319 | =cut |