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1 | package MooseX::Types::Parameterizable; |
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2 | |
3 | use 5.008; |
4 | |
5 | our $VERSION = '0.01'; |
6 | $VERSION = eval $VERSION; |
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7 | |
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8 | use Moose::Util::TypeConstraints; |
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9 | use MooseX::Meta::TypeConstraint::Parameterizable; |
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10 | use MooseX::Types -declare => [qw(Parameterizable)]; |
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11 | |
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12 | =head1 NAME |
13 | |
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14 | MooseX::Types::Parameterizable - Create your own Parameterizable Types. |
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15 | |
16 | =head1 SYNOPSIS |
17 | |
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18 | Within your L<MooseX::Types> declared library module: |
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19 | |
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20 | use Set::Scalar; |
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21 | use MooseX::Types::Parameterizable qw(Parameterizable); |
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22 | use MooseX::Types::Moose qw(Int ); |
23 | use MooseX::Types -declare=>[qw(Set UniqueInt PositiveSet)]; |
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24 | |
25 | subtype Set, |
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26 | as class_type("Set::Scalar"); |
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27 | |
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28 | subtype UniqueInt, |
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29 | as Parameterizable[Int, Set], |
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30 | where { |
31 | my ($int, $set) = @_; |
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32 | return !$set->has($int); |
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33 | }; |
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34 | |
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35 | subtype PositiveSet, |
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36 | as Set, |
37 | where { |
38 | my ($set) = @_; |
39 | return !grep {$_ <0 } $set->members; |
40 | }; |
41 | |
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42 | subtype PositiveUniqueInt, |
43 | as UniqueInt[PositiveSet]; |
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44 | |
45 | my $set = Set::Scalar->new(1,2,3); |
46 | |
47 | UniqueInt([$set])->check(100); ## Okay, 100 isn't in (1,2,3) |
48 | UniqueInt([$set])->check(-99); ## Okay, -99 isn't in (1,2,3) |
49 | UniqueInt([$set])->check(2); ## Not OK, 2 is in (1,2,3) |
50 | |
51 | PositiveUniqueInt([$set])->check(100); ## Okay, 100 isn't in (1,2,3) |
52 | PositiveUniqueInt([$set])->check(-99); ## Not OK, -99 not Positive Int |
53 | PositiveUniqueInt([$set])->check(2); ## Not OK, 2 is in (1,2,3) |
54 | |
55 | my $negative_set = Set::Scalar->new(-1,-2,-3); |
56 | |
57 | UniqueInt([$negative_set])->check(100); ## Throws exception |
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58 | |
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59 | =head1 DESCRIPTION |
60 | |
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61 | A L<MooseX::Types> library for creating parameterizable types. A parameterizable type |
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62 | constraint for all intents and uses is a subclass of a parent type, but adds a |
63 | secondary type parameter which is available to constraint callbacks (such as |
64 | inside the 'where' clause) or in the coercions. |
65 | |
66 | This allows you to create a type that has additional runtime advice, such as a |
67 | set of numbers within which another number must be unique, or allowable ranges |
68 | for a integer, such as in: |
69 | |
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70 | subtype Range, |
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71 | as Dict[max=>Int, min=>Int], |
72 | where { |
73 | my ($range) = @_; |
74 | return $range->{max} > $range->{min}; |
75 | }; |
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76 | |
77 | subtype RangedInt, |
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78 | as Parameterizable[Int, Range], |
79 | where { |
80 | my ($value, $range) = @_; |
81 | return ($value >= $range->{min} && |
82 | $value <= $range->{max}); |
83 | }; |
84 | |
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85 | RangedInt([{min=>10,max=>100}])->check(50); ## OK |
86 | RangedInt([{min=>50, max=>75}])->check(99); ## Not OK, 99 exceeds max |
87 | |
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88 | This throws a hard Moose exception. You'll need to capture it in an eval or |
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89 | related exception catching system (see L<TryCatch> or <Try::Tiny>.) |
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90 | |
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91 | RangedInt([{min=>99, max=>10}])->check(10); ## Not OK, not a valid Range! |
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92 | |
93 | If you can't accept a hard exception here, you'll need to test the constraining |
94 | values first, as in: |
95 | |
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96 | my $range = {min=>99, max=>10}; |
97 | if(my $err = Range->validate($range)) { |
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98 | ## Handle #$err |
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99 | } else { |
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100 | RangedInt($range)->check(99); |
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101 | } |
102 | |
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103 | Please note that for ArrayRef or HashRef parameterizable type constraints, as in the |
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104 | example above, as a convenience we automatically ref the incoming type |
105 | parameters, so that the above could also be written as: |
106 | |
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107 | RangedInt([min=>10,max=>100])->check(50); ## OK |
108 | RangedInt([min=>50, max=>75])->check(99); ## Not OK, 99 exceeds max |
109 | RangedInt([min=>99, max=>10])->check(10); ## Exception, not a valid Range! |
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110 | |
111 | This is the preferred syntax, as it improve readability and adds to the |
112 | conciseness of your type constraint declarations. An exception wil be thrown if |
113 | your type parameters don't match the required reference type. |
114 | |
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115 | Also not that if you 'chain' parameterization results with a method call like: |
116 | |
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117 | TypeConstraint([$ob])->method; |
118 | |
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119 | You need to have the "(...)" around the ArrayRef in the Type Constraint |
120 | parameters. This seems to have something to do with the precendent level of |
121 | "->". Patches or thoughts welcomed. You only need to do this in the above |
122 | case which I imagine is not a very common case. |
123 | |
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124 | ==head2 Subtyping a Parameterizable type constraints |
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125 | |
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126 | When subclassing a parameterizable type you must be careful to match either the |
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127 | required type parameter type constraint, or if re-parameterizing, the new |
128 | type constraints are a subtype of the parent. For example: |
129 | |
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130 | subtype RangedInt, |
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131 | as Parameterizable[Int, Range], |
132 | where { |
133 | my ($value, $range) = @_; |
134 | return ($value >= $range->{min} && |
135 | $value =< $range->{max}); |
136 | }; |
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137 | |
138 | Example subtype with additional constraints: |
139 | |
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140 | subtype PositiveRangedInt, |
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141 | as RangedInt, |
142 | where { |
143 | shift >= 0; |
144 | }; |
145 | |
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146 | Or you could have done the following instead: |
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147 | |
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148 | ## Subtype of Int for positive numbers |
149 | subtype PositiveInt, |
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150 | as Int, |
151 | where { |
152 | my ($value, $range) = @_; |
153 | return $value >= 0; |
154 | }; |
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155 | |
156 | ## subtype Range to re-parameterize Range with subtypes |
157 | subtype PositiveRange, |
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158 | as Range[max=>PositiveInt, min=>PositiveInt]; |
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159 | |
160 | ## create subtype via reparameterizing |
161 | subtype PositiveRangedInt, |
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162 | as RangedInt[PositiveRange]; |
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163 | |
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164 | Notice how re-parameterizing the parameterizable type 'RangedInt' works slightly |
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165 | differently from re-parameterizing 'PositiveRange' Although it initially takes |
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166 | two type constraint values to declare a parameterizable type, should you wish to |
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167 | later re-parameterize it, you only use a subtype of the second type parameter |
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168 | (the parameterizable type constraint) since the first type constraint sets the parent |
169 | type for the parameterizable type. In other words, given the example above, a type |
170 | constraint of 'RangedInt' would have a parent of 'Int', not 'Parameterizable' and for |
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171 | all intends and uses you could stick it wherever you'd need an Int. |
172 | |
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173 | subtype NameAge, |
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174 | as Tuple[Str, Int]; |
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175 | |
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176 | ## re-parameterized subtypes of NameAge containing a Parameterizable Int |
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177 | subtype NameBetween18and35Age, |
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178 | as NameAge[ |
179 | Str, |
180 | PositiveRangedInt[min=>18,max=>35], |
181 | ]; |
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182 | |
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183 | One caveat is that you can't stick an unparameterized parameterizable type inside a |
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184 | structure, such as L<MooseX::Types::Structured> since that would require the |
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185 | ability to convert a 'containing' type constraint into a parameterizable type, which |
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186 | is a capacity we current don't have. |
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187 | |
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188 | =head2 Coercions |
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189 | |
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190 | Parameterizable types have some limited support for coercions. Several things must |
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191 | be kept in mind. The first is that the coercion targets the type constraint |
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192 | which is being made parameterizable, Not the parameterizable type. So for example if you |
193 | create a Parameterizable type like: |
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194 | |
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195 | subtype RequiredAgeInYears, |
196 | as Int; |
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197 | |
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198 | subtype PersonOverAge, |
199 | as Parameterizable[Person, RequiredAgeInYears] |
200 | where { |
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201 | my ($person, $required_years_old) = @_; |
202 | return $person->years_old > $required_years_old; |
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203 | } |
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204 | |
205 | This would validate the following: |
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206 | |
207 | my $person = Person->new(age=>35); |
208 | PersonOverAge([18])->check($person); |
209 | |
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210 | You can then apply the following coercion |
211 | |
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212 | coerce PersonOverAge, |
213 | from Dict[age=>int], |
214 | via {Person->new(%$_)}, |
215 | from Int, |
216 | via {Person->new(age=>$_)}; |
217 | |
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218 | This coercion would then apply to all the following: |
219 | |
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220 | PersonOverAge([18])->check(30); ## via the Int coercion |
221 | PersonOverAge([18])->check({age=>50}); ## via the Dict coercion |
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222 | |
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223 | However, you are not allowed to place coercions on parameterizable types that have |
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224 | had their constraining value filled, nor subtypes of such. For example: |
225 | |
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226 | coerce PersonOverAge[18], |
227 | from DateTime, |
228 | via {$_->years}; |
229 | |
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230 | That would generate a hard exception. This is a limitation for now until I can |
231 | devise a smarter way to cache the generated type constraints. However, I doubt |
232 | it will be a significant limitation, since the general use case is supported. |
233 | |
234 | Lastly, the constraining value is available in the coercion in much the same way |
235 | it is available to the constraint. |
236 | |
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237 | ## Create a type constraint where a Person must be in the set |
238 | subtype PersonInSet, |
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239 | as Parameterizable[Person, PersonSet], |
240 | where { |
241 | my ($person, $person_set) = @_; |
242 | $person_set->find($person); |
243 | } |
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244 | |
245 | coerce PersonInSet, |
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246 | from HashRef, |
247 | via { |
248 | my ($hashref, $person_set) = @_; |
249 | return $person_set->create($hash_ref); |
250 | }; |
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251 | |
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252 | =head2 Recursion |
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253 | |
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254 | TBD |
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255 | |
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256 | =head1 TYPE CONSTRAINTS |
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257 | |
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258 | This type library defines the following constraints. |
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259 | |
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260 | =head2 Parameterizable[ParentTypeConstraint, ParameterizableValueTypeConstraint] |
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261 | |
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262 | Create a subtype of ParentTypeConstraint with a dependency on a value that can |
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263 | pass the ParameterizableValueTypeConstraint. If ParameterizableValueTypeConstraint is empty |
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264 | we default to the 'Any' type constraint (see L<Moose::Util::TypeConstraints>). |
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265 | |
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266 | This creates a type constraint which must be further parameterized at later time |
267 | before it can be used to ->check or ->validate a value. Attempting to do so |
268 | will cause an exception. |
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269 | |
270 | =cut |
271 | |
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272 | Moose::Util::TypeConstraints::get_type_constraint_registry->add_type_constraint( |
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273 | MooseX::Meta::TypeConstraint::Parameterizable->new( |
274 | name => 'MooseX::Types::Parameterizable::Parameterizable', |
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275 | parent => find_type_constraint('Any'), |
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276 | constraint => sub {1}, |
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277 | ) |
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278 | ); |
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279 | |
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280 | =head1 AUTHOR |
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281 | |
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282 | John Napiorkowski, C<< <jjnapiork@cpan.org> >> |
283 | |
284 | =head1 COPYRIGHT & LICENSE |
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285 | |
286 | This program is free software; you can redistribute it and/or modify |
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287 | it under the same terms as Perl itself. |
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288 | |
289 | =cut |
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290 | |
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291 | 1; |