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