also this variable should be available to other script where this env variable is used .

This isn't possible in a straightforward way, as brian_d_foy mentioned. The reason lies in the way environment variables work. Environment variables belong not to a user, or to a "login session," but to a process. Any child process of that process then inherits those variables. So if from your Perl program you call another program through system, qx``, or the piped form of open, then that program will inherit any environment variables that your program has set using %ENV. But any program not launched in that way will not be able to see them without substantial additional work. Also, the follwing code:

open my $fh, "| someotherprog.pl" or die $!;
$ENV{FOO} = 'bar';
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Win32 has a separate notion of "persistent" environment variables stored in the registry. I am not sure how to manipulate them with Perl, but I am fairly certain that modifying %ENV alone will not do it.

Environment variables live in the %ENV hash. You can create them as you like, and the process and its children see that value.

$ENV{TESTDIR} = './t';
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You can't set this value from one process and see it in some other process without some sort of IPC trick, though. If at all possible, you should try to set it before you run the script according to whatever your shell allows.

This is starting to feel like Groundhog Day, one of my favourite movies. :-)

14 hours ago this question was asked: export environment variable from a perl program -- you might like to check out the answers given there.

Phil? Phil Connors?

this variable should be available to other script

If you are brave, and insist on this approach, you can do this with an ugly dot-and-carry method. Assume that your perl script is embedded a wrapper shell (bash-like assumed) script like so:

cd /path/to/script
./myperlscript foo bar rat quux
. ./newvar.sh
./myotherscript
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Where your perl script 'myperlscript' contains (amongst whatever else it needs to do) something like the following:

#! /usr/local/bin/perl

my %new_env = @ARGV;

open OUT, '> newvar.sh' or die "cannot open newvar.sh for output: $!\n
+";
print OUT "#! /bin/sh\n";
print OUT "export $_=$new_env{$_}\n" for keys %new_env;
close OUT;
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That is, the perl script writes the shell script that is the next command to be executed in the outer shell script. By the time ./myotherscript runs, the environment will have been sourced by the script that the perl script wrote beforehand.

But keep in mind that this is a maintenance nightmare, and those who come after you will not venerate your name.

Parent (your script):

#!/usr/local/bin/perl
use strict;
use warnings;

$ENV{foo}="bar";

if (fork == 0){ #child
        exec("./foo.pl");
} else{
        print "I'm the parent $ENV{foo}\n";
}
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Child (other scripts):

#!/usr/local/bin/perl

print "I'm the child $ENV{foo}\n";
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This works because environment is propagated to childs (and filehandles and...).

Search for fork+exec for more information.