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.