I don't think trying to bracket the hires time with lores
[p5sagit/p5-mst-13.2.git] / lib / strict.pm
CommitLineData
a0d0e21e 1package strict;
2
f06db76b 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
55497cff 22casual programming.) Currently, there are three possible things to be
23strict about: "subs", "vars", and "refs".
f06db76b 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
d6fd2b02 37 $file = "STDOUT";
38 print $file "Hi!"; # error; note: no comma after $file
f06db76b 39
cec39fc8 40There is one exception to this rule:
41
42 $bar = \&{'foo'};
43 &$bar;
44
45is allowed so that C<goto &$AUTOLOAD> would not break under stricture.
46
47
f06db76b 48=item C<strict vars>
49
50This generates a compile-time error if you access a variable that wasn't
17f410f9 51declared via "our" or C<use vars>,
52localized via C<my()>, or wasn't fully qualified. Because this is to avoid
f06db76b 53variable suicide problems and subtle dynamic scoping issues, a merely
54local() variable isn't good enough. See L<perlfunc/my> and
55L<perlfunc/local>.
56
57 use strict 'vars';
58 $X::foo = 1; # ok, fully qualified
59 my $foo = 10; # ok, my() var
60 local $foo = 9; # blows up
61
535b5725 62 package Cinna;
17f410f9 63 our $bar; # Declares $bar in current package
535b5725 64 $bar = 'HgS'; # ok, global declared via pragma
65
f06db76b 66The local() generated a compile-time error because you just touched a global
67name without fully qualifying it.
68
3ce0d271 69Because of their special use by sort(), the variables $a and $b are
70exempted from this check.
71
f06db76b 72=item C<strict subs>
73
cb1a09d0 74This disables the poetry optimization, generating a compile-time error if
75you try to use a bareword identifier that's not a subroutine, unless it
1fef88e7 76appears in curly braces or on the left hand side of the "=E<gt>" symbol.
cb1a09d0 77
f06db76b 78
79 use strict 'subs';
80 $SIG{PIPE} = Plumber; # blows up
cb1a09d0 81 $SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok
82 $SIG{PIPE} = \&Plumber; # preferred form
83
84
f06db76b 85
86=back
87
ee580363 88See L<perlmodlib/Pragmatic Modules>.
f06db76b 89
90
91=cut
92
d6a466d7 93$strict::VERSION = "1.02";
4682965a 94
95my %bitmask = (
96refs => 0x00000002,
97subs => 0x00000200,
98vars => 0x00000400
99);
100
a0d0e21e 101sub bits {
102 my $bits = 0;
20408e3c 103 foreach my $s (@_){ $bits |= $bitmask{$s} || 0; };
a0d0e21e 104 $bits;
105}
106
107sub import {
108 shift;
55497cff 109 $^H |= bits(@_ ? @_ : qw(refs subs vars));
a0d0e21e 110}
111
112sub unimport {
113 shift;
55497cff 114 $^H &= ~ bits(@_ ? @_ : qw(refs subs vars));
a0d0e21e 115}
116
1171;