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a0d0e21e LW |
1 | package strict; |
2 | ||
f06db76b AD |
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 | |
55497cff | 22 | casual programming.) Currently, there are three possible things to be |
23 | strict about: "subs", "vars", and "refs". | |
f06db76b AD |
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 | |
535b5725 | 41 | declared via C<use vars>, |
f06db76b AD |
42 | localized via C<my()> or wasn't fully qualified. Because this is to avoid |
43 | variable suicide problems and subtle dynamic scoping issues, a merely | |
44 | local() variable isn't good enough. See L<perlfunc/my> and | |
45 | L<perlfunc/local>. | |
46 | ||
47 | use strict 'vars'; | |
48 | $X::foo = 1; # ok, fully qualified | |
49 | my $foo = 10; # ok, my() var | |
50 | local $foo = 9; # blows up | |
51 | ||
535b5725 TP |
52 | package Cinna; |
53 | use vars qw/ $bar /; # Declares $bar in current package | |
54 | $bar = 'HgS'; # ok, global declared via pragma | |
55 | ||
f06db76b AD |
56 | The local() generated a compile-time error because you just touched a global |
57 | name without fully qualifying it. | |
58 | ||
3ce0d271 GS |
59 | Because of their special use by sort(), the variables $a and $b are |
60 | exempted from this check. | |
61 | ||
f06db76b AD |
62 | =item C<strict subs> |
63 | ||
cb1a09d0 AD |
64 | This disables the poetry optimization, generating a compile-time error if |
65 | you try to use a bareword identifier that's not a subroutine, unless it | |
1fef88e7 | 66 | appears in curly braces or on the left hand side of the "=E<gt>" symbol. |
cb1a09d0 | 67 | |
f06db76b AD |
68 | |
69 | use strict 'subs'; | |
70 | $SIG{PIPE} = Plumber; # blows up | |
cb1a09d0 AD |
71 | $SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok |
72 | $SIG{PIPE} = \&Plumber; # preferred form | |
73 | ||
74 | ||
f06db76b AD |
75 | |
76 | =back | |
77 | ||
ee580363 | 78 | See L<perlmodlib/Pragmatic Modules>. |
f06db76b AD |
79 | |
80 | ||
81 | =cut | |
82 | ||
4682965a MB |
83 | $strict::VERSION = "1.01"; |
84 | ||
85 | my %bitmask = ( | |
86 | refs => 0x00000002, | |
87 | subs => 0x00000200, | |
88 | vars => 0x00000400 | |
89 | ); | |
90 | ||
a0d0e21e LW |
91 | sub bits { |
92 | my $bits = 0; | |
20408e3c | 93 | foreach my $s (@_){ $bits |= $bitmask{$s} || 0; }; |
a0d0e21e LW |
94 | $bits; |
95 | } | |
96 | ||
97 | sub import { | |
98 | shift; | |
55497cff | 99 | $^H |= bits(@_ ? @_ : qw(refs subs vars)); |
a0d0e21e LW |
100 | } |
101 | ||
102 | sub unimport { | |
103 | shift; | |
55497cff | 104 | $^H &= ~ bits(@_ ? @_ : qw(refs subs vars)); |
a0d0e21e LW |
105 | } |
106 | ||
107 | 1; |