use Env;

use Env qw(var1 var2 ...);

Internally, Env uses an import function that ties suitably named environment variables to global Perl variables with the same names. By default, it ties all variables yielded by keys %ENV. A "suitable" environment has a name that begins with an alphabetic character and contains only alphanumeric characters or underscores.

When use Env is invoked with arguments, the arguments are interpreted as a list of environment variables to tie, but the variables don't have to exist yet. After a variable has been tied, you can use it like a normal variable, accessing or changing its value.

You untie a variable by setting its value to undef.

8.63. English		8.65. Errno