1 | package Env;
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2 |
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3 | our $VERSION = '1.00';
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4 |
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5 | =head1 NAME
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6 |
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7 | Env - perl module that imports environment variables as scalars or arrays
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8 |
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9 | =head1 SYNOPSIS
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10 |
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11 | use Env;
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12 | use Env qw(PATH HOME TERM);
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13 | use Env qw($SHELL @LD_LIBRARY_PATH);
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14 |
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15 | =head1 DESCRIPTION
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16 |
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17 | Perl maintains environment variables in a special hash named C<%ENV>. For
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18 | when this access method is inconvenient, the Perl module C<Env> allows
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19 | environment variables to be treated as scalar or array variables.
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20 |
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21 | The C<Env::import()> function ties environment variables with suitable
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22 | names to global Perl variables with the same names. By default it
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23 | ties all existing environment variables (C<keys %ENV>) to scalars. If
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24 | the C<import> function receives arguments, it takes them to be a list of
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25 | variables to tie; it's okay if they don't yet exist. The scalar type
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26 | prefix '$' is inferred for any element of this list not prefixed by '$'
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27 | or '@'. Arrays are implemented in terms of C<split> and C<join>, using
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28 | C<$Config::Config{path_sep}> as the delimiter.
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29 |
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30 | After an environment variable is tied, merely use it like a normal variable.
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31 | You may access its value
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32 |
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33 | @path = split(/:/, $PATH);
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34 | print join("\n", @LD_LIBRARY_PATH), "\n";
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35 |
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36 | or modify it
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37 |
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38 | $PATH .= ":.";
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39 | push @LD_LIBRARY_PATH, $dir;
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40 |
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41 | however you'd like. Bear in mind, however, that each access to a tied array
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42 | variable requires splitting the environment variable's string anew.
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43 |
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44 | The code:
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45 |
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46 | use Env qw(@PATH);
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47 | push @PATH, '.';
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48 |
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49 | is equivalent to:
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50 |
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51 | use Env qw(PATH);
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52 | $PATH .= ":.";
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53 |
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54 | except that if C<$ENV{PATH}> started out empty, the second approach leaves
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55 | it with the (odd) value "C<:.>", but the first approach leaves it with "C<.>".
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56 |
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57 | To remove a tied environment variable from
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58 | the environment, assign it the undefined value
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59 |
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60 | undef $PATH;
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61 | undef @LD_LIBRARY_PATH;
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62 |
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63 | =head1 LIMITATIONS
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64 |
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65 | On VMS systems, arrays tied to environment variables are read-only. Attempting
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66 | to change anything will cause a warning.
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67 |
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68 | =head1 AUTHOR
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69 |
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70 | Chip Salzenberg E<lt>F<[email protected]>E<gt>
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71 | and
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72 | Gregor N. Purdy E<lt>F<[email protected]>E<gt>
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73 |
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74 | =cut
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75 |
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76 | sub import {
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77 | my ($callpack) = caller(0);
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78 | my $pack = shift;
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79 | my @vars = grep /^[\$\@]?[A-Za-z_]\w*$/, (@_ ? @_ : keys(%ENV));
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80 | return unless @vars;
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81 |
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82 | @vars = map { m/^[\$\@]/ ? $_ : '$'.$_ } @vars;
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83 |
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84 | eval "package $callpack; use vars qw(" . join(' ', @vars) . ")";
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85 | die $@ if $@;
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86 | foreach (@vars) {
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87 | my ($type, $name) = m/^([\$\@])(.*)$/;
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88 | if ($type eq '$') {
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89 | tie ${"${callpack}::$name"}, Env, $name;
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90 | } else {
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91 | if ($^O eq 'VMS') {
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92 | tie @{"${callpack}::$name"}, Env::Array::VMS, $name;
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93 | } else {
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94 | tie @{"${callpack}::$name"}, Env::Array, $name;
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95 | }
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96 | }
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97 | }
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98 | }
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99 |
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100 | sub TIESCALAR {
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101 | bless \($_[1]);
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102 | }
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103 |
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104 | sub FETCH {
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105 | my ($self) = @_;
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106 | $ENV{$$self};
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107 | }
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108 |
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109 | sub STORE {
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110 | my ($self, $value) = @_;
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111 | if (defined($value)) {
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112 | $ENV{$$self} = $value;
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113 | } else {
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114 | delete $ENV{$$self};
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115 | }
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116 | }
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117 |
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118 | ######################################################################
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119 |
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120 | package Env::Array;
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121 |
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122 | use Config;
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123 | use Tie::Array;
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124 |
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125 | @ISA = qw(Tie::Array);
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126 |
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127 | my $sep = $Config::Config{path_sep};
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128 |
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129 | sub TIEARRAY {
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130 | bless \($_[1]);
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131 | }
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132 |
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133 | sub FETCHSIZE {
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134 | my ($self) = @_;
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135 | my @temp = split($sep, $ENV{$$self});
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136 | return scalar(@temp);
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137 | }
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138 |
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139 | sub STORESIZE {
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140 | my ($self, $size) = @_;
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141 | my @temp = split($sep, $ENV{$$self});
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142 | $#temp = $size - 1;
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143 | $ENV{$$self} = join($sep, @temp);
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144 | }
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145 |
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146 | sub CLEAR {
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147 | my ($self) = @_;
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148 | $ENV{$$self} = '';
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149 | }
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150 |
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151 | sub FETCH {
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152 | my ($self, $index) = @_;
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153 | return (split($sep, $ENV{$$self}))[$index];
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154 | }
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155 |
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156 | sub STORE {
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157 | my ($self, $index, $value) = @_;
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158 | my @temp = split($sep, $ENV{$$self});
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159 | $temp[$index] = $value;
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160 | $ENV{$$self} = join($sep, @temp);
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161 | return $value;
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162 | }
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163 |
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164 | sub PUSH {
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165 | my $self = shift;
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166 | my @temp = split($sep, $ENV{$$self});
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167 | push @temp, @_;
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168 | $ENV{$$self} = join($sep, @temp);
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169 | return scalar(@temp);
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170 | }
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171 |
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172 | sub POP {
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173 | my ($self) = @_;
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174 | my @temp = split($sep, $ENV{$$self});
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175 | my $result = pop @temp;
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176 | $ENV{$$self} = join($sep, @temp);
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177 | return $result;
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178 | }
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179 |
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180 | sub UNSHIFT {
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181 | my $self = shift;
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182 | my @temp = split($sep, $ENV{$$self});
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183 | my $result = unshift @temp, @_;
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184 | $ENV{$$self} = join($sep, @temp);
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185 | return $result;
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186 | }
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187 |
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188 | sub SHIFT {
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189 | my ($self) = @_;
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190 | my @temp = split($sep, $ENV{$$self});
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191 | my $result = shift @temp;
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192 | $ENV{$$self} = join($sep, @temp);
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193 | return $result;
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194 | }
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195 |
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196 | sub SPLICE {
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197 | my $self = shift;
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198 | my $offset = shift;
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199 | my $length = shift;
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200 | my @temp = split($sep, $ENV{$$self});
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201 | if (wantarray) {
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202 | my @result = splice @temp, $self, $offset, $length, @_;
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203 | $ENV{$$self} = join($sep, @temp);
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204 | return @result;
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205 | } else {
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206 | my $result = scalar splice @temp, $offset, $length, @_;
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207 | $ENV{$$self} = join($sep, @temp);
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208 | return $result;
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209 | }
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210 | }
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211 |
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212 | ######################################################################
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213 |
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214 | package Env::Array::VMS;
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215 | use Tie::Array;
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216 |
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217 | @ISA = qw(Tie::Array);
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218 |
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219 | sub TIEARRAY {
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220 | bless \($_[1]);
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221 | }
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222 |
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223 | sub FETCHSIZE {
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224 | my ($self) = @_;
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225 | my $i = 0;
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226 | while ($i < 127 and defined $ENV{$$self . ';' . $i}) { $i++; };
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227 | return $i;
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228 | }
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229 |
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230 | sub FETCH {
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231 | my ($self, $index) = @_;
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232 | return $ENV{$$self . ';' . $index};
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233 | }
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234 |
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235 | 1;
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