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CentOS 7.0 - man page for env (centos section 3)

Env(3)			       User Contributed Perl Documentation			   Env(3)

       Env - perl module that imports environment variables as scalars or arrays

	   use Env;
	   use Env qw(PATH HOME TERM);
	   use Env qw($SHELL @LD_LIBRARY_PATH);

       Perl maintains environment variables in a special hash named %ENV.  For when this access
       method is inconvenient, the Perl module "Env" allows environment variables to be treated
       as scalar or array variables.

       The "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
       ("keys %ENV") to scalars.  If the "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 "split" and "join", using $Config::Config{path_sep} as the

       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 $ENV{PATH} started out empty, the second approach leaves it with the (odd)
       value "":."", but the first approach leaves it with ""."".

       To remove a tied environment variable from the environment, assign it the undefined value

	   undef $PATH;
	   undef @LD_LIBRARY_PATH;

       On VMS systems, arrays tied to environment variables are read-only. Attempting to change
       anything will cause a warning.

       Chip Salzenberg <chip@fin.uucp> and Gregor N. Purdy <gregor@focusresearch.com>

perl v5.16.3				    2013-03-02					   Env(3)

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