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[ PATCH 5.004_64 ] Integrated regression tests for compiler
[perl5.git] / lib / strict.pm
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1package strict;
2
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3=head1 NAME
4
5strict - 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
20If 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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22casual programming.) Currently, there are three possible things to be
23strict about: "subs", "vars", and "refs".
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24
25=over 6
26
27=item C<strict refs>
28
29This generates a runtime error if you
30use 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
40This generates a compile-time error if you access a variable that wasn't
41localized via C<my()> or wasn't fully qualified. Because this is to avoid
42variable suicide problems and subtle dynamic scoping issues, a merely
43local() variable isn't good enough. See L<perlfunc/my> and
44L<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
51The local() generated a compile-time error because you just touched a global
52name without fully qualifying it.
53
54=item C<strict subs>
55
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56This disables the poetry optimization, generating a compile-time error if
57you try to use a bareword identifier that's not a subroutine, unless it
1fef88e7 58appears in curly braces or on the left hand side of the "=E<gt>" symbol.
cb1a09d0 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
70See L<perlmod/Pragmatic Modules>.
71
72
73=cut
74
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75sub bits {
76 my $bits = 0;
7a4c00b4 77 my $sememe;
a0d0e21e 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
86sub import {
87 shift;
55497cff 88 $^H |= bits(@_ ? @_ : qw(refs subs vars));
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89}
90
91sub unimport {
92 shift;
55497cff 93 $^H &= ~ bits(@_ ? @_ : qw(refs subs vars));
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94}
95
961;