Env(3p) | Perl Programmers Reference Guide | Env(3p)

# 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>

2024-05-14 | perl v5.40.1