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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 |
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37 | $file = "STDOUT"; |
38 | print $file "Hi!"; # error; note: no comma after $file |
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39 | |
40 | =item C<strict vars> |
41 | |
42 | This generates a compile-time error if you access a variable that wasn't |
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43 | declared via "our" or C<use vars>, |
44 | localized via C<my()>, or wasn't fully qualified. Because this is to avoid |
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45 | variable suicide problems and subtle dynamic scoping issues, a merely |
46 | local() variable isn't good enough. See L<perlfunc/my> and |
47 | L<perlfunc/local>. |
48 | |
49 | use strict 'vars'; |
50 | $X::foo = 1; # ok, fully qualified |
51 | my $foo = 10; # ok, my() var |
52 | local $foo = 9; # blows up |
53 | |
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54 | package Cinna; |
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55 | our $bar; # Declares $bar in current package |
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56 | $bar = 'HgS'; # ok, global declared via pragma |
57 | |
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58 | The local() generated a compile-time error because you just touched a global |
59 | name without fully qualifying it. |
60 | |
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61 | Because of their special use by sort(), the variables $a and $b are |
62 | exempted from this check. |
63 | |
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64 | =item C<strict subs> |
65 | |
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66 | This disables the poetry optimization, generating a compile-time error if |
67 | you try to use a bareword identifier that's not a subroutine, unless it |
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68 | appears in curly braces or on the left hand side of the "=E<gt>" symbol. |
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69 | |
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70 | |
71 | use strict 'subs'; |
72 | $SIG{PIPE} = Plumber; # blows up |
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73 | $SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok |
74 | $SIG{PIPE} = \&Plumber; # preferred form |
75 | |
76 | |
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77 | |
78 | =back |
79 | |
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80 | See L<perlmodlib/Pragmatic Modules>. |
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81 | |
82 | |
83 | =cut |
84 | |
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85 | $strict::VERSION = "1.01"; |
86 | |
87 | my %bitmask = ( |
88 | refs => 0x00000002, |
89 | subs => 0x00000200, |
90 | vars => 0x00000400 |
91 | ); |
92 | |
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93 | sub bits { |
94 | my $bits = 0; |
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95 | foreach my $s (@_){ $bits |= $bitmask{$s} || 0; }; |
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96 | $bits; |
97 | } |
98 | |
99 | sub import { |
100 | shift; |
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101 | $^H |= bits(@_ ? @_ : qw(refs subs vars)); |
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102 | } |
103 | |
104 | sub unimport { |
105 | shift; |
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106 | $^H &= ~ bits(@_ ? @_ : qw(refs subs vars)); |
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107 | } |
108 | |
109 | 1; |