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1 | package vars; |
2 | |
3 | =head1 NAME |
4 | |
5 | vars - Perl pragma to predeclare global variable names |
6 | |
7 | =head1 SYNOPSIS |
8 | |
9 | use vars qw($frob @mung %seen); |
10 | |
11 | =head1 DESCRIPTION |
12 | |
13 | This will predeclare all the variables whose names are |
14 | in the list, allowing you to use them under "use strict", and |
15 | disabling any typo warnings. |
16 | |
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17 | Unlike pragmas that affect the C<$^H> hints variable, the C<use vars> and |
18 | C<use subs> declarations are not BLOCK-scoped. They are thus effective |
19 | for the entire file in which they appear. You may not rescind such |
20 | declarations with C<no vars> or C<no subs>. |
21 | |
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22 | Packages such as the B<AutoLoader> and B<SelfLoader> that delay loading |
23 | of subroutines within packages can create problems with package lexicals |
24 | defined using C<my()>. While the B<vars> pragma cannot duplicate the |
25 | effect of package lexicals (total transparency outside of the package), |
26 | it can act as an acceptable substitute by pre-declaring global symbols, |
27 | ensuring their availability to to the later-loaded routines. |
28 | |
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29 | See L<perlmod/Pragmatic Modules>. |
30 | |
31 | =cut |
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32 | |
33 | require 5.002; |
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34 | use Carp; |
35 | |
36 | sub import { |
37 | my $callpack = caller; |
38 | my ($pack, @imports, $sym, $ch) = @_; |
39 | foreach $sym (@imports) { |
40 | croak "Can't declare another package's variables" if $sym =~ /::/; |
41 | ($ch, $sym) = unpack('a1a*', $sym); |
42 | *{"${callpack}::$sym"} = |
43 | ( $ch eq "\$" ? \$ {"${callpack}::$sym"} |
44 | : $ch eq "\@" ? \@ {"${callpack}::$sym"} |
45 | : $ch eq "\%" ? \% {"${callpack}::$sym"} |
46 | : $ch eq "\*" ? \* {"${callpack}::$sym"} |
47 | : $ch eq "\&" ? \& {"${callpack}::$sym"} |
48 | : croak "'$ch$sym' is not a valid variable name\n"); |
49 | } |
50 | }; |
51 | |
52 | 1; |