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1 | package strict; |
2 | |
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3 | =head1 NAME |
4 | |
5 | strict - Perl pragma to restrict unsafe constructs |
6 | |
7 | =head1 SYNOPSIS |
8 | |
9 | use strict; |
10 | |
11 | use strict "vars"; |
12 | use strict "refs"; |
13 | use strict "subs"; |
14 | |
15 | use strict; |
16 | no strict "vars"; |
17 | |
18 | =head1 DESCRIPTION |
19 | |
20 | If no import list is supplied, all possible restrictions are assumed. |
21 | (This is the safest mode to operate in, but is sometimes too strict for |
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22 | casual programming.) Currently, there are three possible things to be |
23 | strict about: "subs", "vars", and "refs". |
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24 | |
25 | =over 6 |
26 | |
27 | =item C<strict refs> |
28 | |
29 | This generates a runtime error if you |
30 | use symbolic references (see L<perlref>). |
31 | |
32 | use strict 'refs'; |
33 | $ref = \$foo; |
34 | print $$ref; # ok |
35 | $ref = "foo"; |
36 | print $$ref; # runtime error; normally ok |
37 | |
38 | =item C<strict vars> |
39 | |
40 | This generates a compile-time error if you access a variable that wasn't |
41 | localized via C<my()> or wasn't fully qualified. Because this is to avoid |
42 | variable suicide problems and subtle dynamic scoping issues, a merely |
43 | local() variable isn't good enough. See L<perlfunc/my> and |
44 | L<perlfunc/local>. |
45 | |
46 | use strict 'vars'; |
47 | $X::foo = 1; # ok, fully qualified |
48 | my $foo = 10; # ok, my() var |
49 | local $foo = 9; # blows up |
50 | |
51 | The local() generated a compile-time error because you just touched a global |
52 | name without fully qualifying it. |
53 | |
54 | =item C<strict subs> |
55 | |
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56 | This disables the poetry optimization, generating a compile-time error if |
57 | you try to use a bareword identifier that's not a subroutine, unless it |
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58 | appears in curly braces or on the left hand side of the "=E<gt>" symbol. |
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59 | |
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60 | |
61 | use strict 'subs'; |
62 | $SIG{PIPE} = Plumber; # blows up |
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63 | $SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok |
64 | $SIG{PIPE} = \&Plumber; # preferred form |
65 | |
66 | |
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67 | |
68 | =back |
69 | |
70 | See L<perlmod/Pragmatic Modules>. |
71 | |
72 | |
73 | =cut |
74 | |
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75 | sub bits { |
76 | my $bits = 0; |
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77 | my $sememe; |
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78 | foreach $sememe (@_) { |
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79 | $bits |= 0x00000002, next if $sememe eq 'refs'; |
80 | $bits |= 0x00000200, next if $sememe eq 'subs'; |
81 | $bits |= 0x00000400, next if $sememe eq 'vars'; |
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82 | } |
83 | $bits; |
84 | } |
85 | |
86 | sub import { |
87 | shift; |
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88 | $^H |= bits(@_ ? @_ : qw(refs subs vars)); |
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89 | } |
90 | |
91 | sub unimport { |
92 | shift; |
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93 | $^H &= ~ bits(@_ ? @_ : qw(refs subs vars)); |
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94 | } |
95 | |
96 | 1; |