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package Env;
our $VERSION = '1.04';
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=head1 NAME
Env - perl module that imports environment variables as scalars or arrays
=head1 SYNOPSIS
    use Env;
    use Env qw(PATH HOME TERM);
    use Env qw($SHELL @LD_LIBRARY_PATH);
=head1 DESCRIPTION
Perl maintains environment variables in a special hash named C<%ENV>.  For
when this access method is inconvenient, the Perl module C<Env> allows
environment variables to be treated as scalar or array variables.
The C<Env::import()> function ties environment variables with suitable
names to global Perl variables with the same names.  By default it
ties all existing environment variables (C<keys %ENV>) to scalars.  If
the C<import> function receives arguments, it takes them to be a list of
variables to tie; it's okay if they don't yet exist. The scalar type
prefix '$' is inferred for any element of this list not prefixed by '$'
or '@'. Arrays are implemented in terms of C<split> and C<join>, using
C<$Config::Config{path_sep}> as the delimiter.
After an environment variable is tied, merely use it like a normal variable.
You may access its value 
    @path = split(/:/, $PATH);
    print join("\n", @LD_LIBRARY_PATH), "\n";
or modify it
    $PATH .= ":.";
    push @LD_LIBRARY_PATH, $dir;
however you'd like. Bear in mind, however, that each access to a tied array
variable requires splitting the environment variable's string anew.
The code:
    use Env qw(@PATH);
    push @PATH, '.';
is equivalent to:
    use Env qw(PATH);
    $PATH .= ":.";
except that if C<$ENV{PATH}> started out empty, the second approach leaves
it with the (odd) value "C<:.>", but the first approach leaves it with "C<.>".
To remove a tied environment variable from
the environment, assign it the undefined value
    undef $PATH;
    undef @LD_LIBRARY_PATH;
=head1 LIMITATIONS
On VMS systems, arrays tied to environment variables are read-only. Attempting
to change anything will cause a warning.
=head1 AUTHOR
Chip Salzenberg E<lt>F<chip@fin.uucp>E<gt>
and
Gregor N. Purdy E<lt>F<gregor@focusresearch.com>E<gt>
=cut
sub import {
    my ($callpack) = caller(0);
    my $pack = shift;
    my @vars = grep /^[\$\@]?[A-Za-z_]\w*$/, (@_ ? @_ : keys(%ENV));
    return unless @vars;
    @vars = map { m/^[\$\@]/ ? $_ : '$'.$_ } @vars;
    eval "package $callpack; use vars qw(" . join(' ', @vars) . ")";
    die $@ if $@;
    foreach (@vars) {
        my ($type, $name) = m/^([\$\@])(.*)$/;
        if ($type eq '$') {
            tie ${"${callpack}::$name"}, Env, $name;
        } else {
            if ($^O eq 'VMS') {
                tie @{"${callpack}::$name"}, Env::Array::VMS, $name;
            } else {
                tie @{"${callpack}::$name"}, Env::Array, $name;
            }
        }
    }
}
sub TIESCALAR {
    bless \($_[1]);
}
sub FETCH {
    my ($self) = @_;
    $ENV{$$self};
}
sub STORE {
    my ($self, $value) = @_;
    if (defined($value)) {
        $ENV{$$self} = $value;
    } else {
        delete $ENV{$$self};
    }
}
######################################################################
package Env::Array;
  
use Config;
use Tie::Array;
@ISA = qw(Tie::Array);
my $sep = $Config::Config{path_sep};
sub TIEARRAY {
    bless \($_[1]);
}
sub FETCHSIZE {
    my ($self) = @_;
    return 1 + scalar(() = $ENV{$$self} =~ /\Q$sep\E/g);
}
sub STORESIZE {
    my ($self, $size) = @_;
    my @temp = split($sep, $ENV{$$self});
    $#temp = $size - 1;
    $ENV{$$self} = join($sep, @temp);
}
sub CLEAR {
    my ($self) = @_;
    $ENV{$$self} = '';
}
sub FETCH {
    my ($self, $index) = @_;
    return (split($sep, $ENV{$$self}))[$index];
}
sub STORE {
    my ($self, $index, $value) = @_;
    my @temp = split($sep, $ENV{$$self});
    $temp[$index] = $value;
    $ENV{$$self} = join($sep, @temp);
    return $value;
}
sub EXISTS {
    my ($self, $index) = @_;
    return $index < $self->FETCHSIZE;
}
sub DELETE {
    my ($self, $index) = @_;
    my @temp = split($sep, $ENV{$$self});
    my $value = splice(@temp, $index, 1, ());
    $ENV{$$self} = join($sep, @temp);
    return $value;
}
sub PUSH {
    my $self = shift;
    my @temp = split($sep, $ENV{$$self});
    push @temp, @_;
    $ENV{$$self} = join($sep, @temp);
    return scalar(@temp);
}
sub POP {
    my ($self) = @_;
    my @temp = split($sep, $ENV{$$self});
    my $result = pop @temp;
    $ENV{$$self} = join($sep, @temp);
    return $result;
}
sub UNSHIFT {
    my $self = shift;
    my @temp = split($sep, $ENV{$$self});
    my $result = unshift @temp, @_;
    $ENV{$$self} = join($sep, @temp);
    return $result;
}
sub SHIFT {
    my ($self) = @_;
    my @temp = split($sep, $ENV{$$self});
    my $result = shift @temp;
    $ENV{$$self} = join($sep, @temp);
    return $result;
}
sub SPLICE {
    my $self = shift;
    my $offset = shift;
    my $length = shift;
    my @temp = split($sep, $ENV{$$self});
    if (wantarray) {
        my @result = splice @temp, $offset, $length, @_;
        $ENV{$$self} = join($sep, @temp);
        return @result;
    } else {
        my $result = scalar splice @temp, $offset, $length, @_;
        $ENV{$$self} = join($sep, @temp);
        return $result;
    }
}
######################################################################
package Env::Array::VMS;
use Tie::Array;
@ISA = qw(Tie::Array);
  
sub TIEARRAY {
    bless \($_[1]);
}
sub FETCHSIZE {
    my ($self) = @_;
    my $i = 0;
    while ($i < 127 and defined $ENV{$$self . ';' . $i}) { $i++; };
    return $i;
}
sub FETCH {
    my ($self, $index) = @_;
    return $ENV{$$self . ';' . $index};
}
sub EXISTS {
    my ($self, $index) = @_;
    return $index < $self->FETCHSIZE;
}
sub DELETE { }
1;