| 1 |
package strict; |
| 2 |
|
| 3 |
$strict::VERSION = "1.03"; |
| 4 |
|
| 5 |
my %bitmask = ( |
| 6 |
refs => 0x00000002, |
| 7 |
subs => 0x00000200, |
| 8 |
vars => 0x00000400 |
| 9 |
); |
| 10 |
|
| 11 |
sub bits { |
| 12 |
my $bits = 0; |
| 13 |
my @wrong; |
| 14 |
foreach my $s (@_) { |
| 15 |
push @wrong, $s unless exists $bitmask{$s}; |
| 16 |
$bits |= $bitmask{$s} || 0; |
| 17 |
} |
| 18 |
if (@wrong) { |
| 19 |
require Carp; |
| 20 |
Carp::croak("Unknown 'strict' tag(s) '@wrong'"); |
| 21 |
} |
| 22 |
$bits; |
| 23 |
} |
| 24 |
|
| 25 |
my $default_bits = bits(qw(refs subs vars)); |
| 26 |
|
| 27 |
sub import { |
| 28 |
shift; |
| 29 |
$^H |= @_ ? bits(@_) : $default_bits; |
| 30 |
} |
| 31 |
|
| 32 |
sub unimport { |
| 33 |
shift; |
| 34 |
$^H &= ~ (@_ ? bits(@_) : $default_bits); |
| 35 |
} |
| 36 |
|
| 37 |
1; |
| 38 |
__END__ |
| 39 |
|
| 40 |
=head1 NAME |
| 41 |
|
| 42 |
strict - Perl pragma to restrict unsafe constructs |
| 43 |
|
| 44 |
=head1 SYNOPSIS |
| 45 |
|
| 46 |
use strict; |
| 47 |
|
| 48 |
use strict "vars"; |
| 49 |
use strict "refs"; |
| 50 |
use strict "subs"; |
| 51 |
|
| 52 |
use strict; |
| 53 |
no strict "vars"; |
| 54 |
|
| 55 |
=head1 DESCRIPTION |
| 56 |
|
| 57 |
If no import list is supplied, all possible restrictions are assumed. |
| 58 |
(This is the safest mode to operate in, but is sometimes too strict for |
| 59 |
casual programming.) Currently, there are three possible things to be |
| 60 |
strict about: "subs", "vars", and "refs". |
| 61 |
|
| 62 |
=over 6 |
| 63 |
|
| 64 |
=item C<strict refs> |
| 65 |
|
| 66 |
This generates a runtime error if you |
| 67 |
use symbolic references (see L<perlref>). |
| 68 |
|
| 69 |
use strict 'refs'; |
| 70 |
$ref = \$foo; |
| 71 |
print $$ref; # ok |
| 72 |
$ref = "foo"; |
| 73 |
print $$ref; # runtime error; normally ok |
| 74 |
$file = "STDOUT"; |
| 75 |
print $file "Hi!"; # error; note: no comma after $file |
| 76 |
|
| 77 |
There is one exception to this rule: |
| 78 |
|
| 79 |
$bar = \&{'foo'}; |
| 80 |
&$bar; |
| 81 |
|
| 82 |
is allowed so that C<goto &$AUTOLOAD> would not break under stricture. |
| 83 |
|
| 84 |
|
| 85 |
=item C<strict vars> |
| 86 |
|
| 87 |
This generates a compile-time error if you access a variable that wasn't |
| 88 |
declared via C<our> or C<use vars>, |
| 89 |
localized via C<my()>, or wasn't fully qualified. Because this is to avoid |
| 90 |
variable suicide problems and subtle dynamic scoping issues, a merely |
| 91 |
local() variable isn't good enough. See L<perlfunc/my> and |
| 92 |
L<perlfunc/local>. |
| 93 |
|
| 94 |
use strict 'vars'; |
| 95 |
$X::foo = 1; # ok, fully qualified |
| 96 |
my $foo = 10; # ok, my() var |
| 97 |
local $foo = 9; # blows up |
| 98 |
|
| 99 |
package Cinna; |
| 100 |
our $bar; # Declares $bar in current package |
| 101 |
$bar = 'HgS'; # ok, global declared via pragma |
| 102 |
|
| 103 |
The local() generated a compile-time error because you just touched a global |
| 104 |
name without fully qualifying it. |
| 105 |
|
| 106 |
Because of their special use by sort(), the variables $a and $b are |
| 107 |
exempted from this check. |
| 108 |
|
| 109 |
=item C<strict subs> |
| 110 |
|
| 111 |
This disables the poetry optimization, generating a compile-time error if |
| 112 |
you try to use a bareword identifier that's not a subroutine, unless it |
| 113 |
is a simple identifier (no colons) and that it appears in curly braces or |
| 114 |
on the left hand side of the C<< => >> symbol. |
| 115 |
|
| 116 |
use strict 'subs'; |
| 117 |
$SIG{PIPE} = Plumber; # blows up |
| 118 |
$SIG{PIPE} = "Plumber"; # just fine: quoted string is always ok |
| 119 |
$SIG{PIPE} = \&Plumber; # preferred form |
| 120 |
|
| 121 |
=back |
| 122 |
|
| 123 |
See L<perlmodlib/Pragmatic Modules>. |
| 124 |
|
| 125 |
=head1 HISTORY |
| 126 |
|
| 127 |
C<strict 'subs'>, with Perl 5.6.1, erroneously permitted to use an unquoted |
| 128 |
compound identifier (e.g. C<Foo::Bar>) as a hash key (before C<< => >> or |
| 129 |
inside curlies), but without forcing it always to a literal string. |
| 130 |
|
| 131 |
Starting with Perl 5.8.1 strict is strict about its restrictions: |
| 132 |
if unknown restrictions are used, the strict pragma will abort with |
| 133 |
|
| 134 |
Unknown 'strict' tag(s) '...' |
| 135 |
|
| 136 |
=cut |
