Env(3perl)             Perl Programmers Reference Guide             Env(3perl)


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

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

DESCRIPTION
       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 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 .= ":/any/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, '/any/path';

       is almost equivalent to:

           use Env qw(PATH);
           $PATH .= ":/any/path";

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

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

           undef $PATH;
           undef @LD_LIBRARY_PATH;

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

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

perl v5.38.2                      2024-02-11                        Env(3perl)