Thanks for looking into my script, I got it was I was looking for, the script was good with few mistakes but the main problem was that my array was treating the complete list of ip and subnets as 1 element so had to split them and everything worked out fine

final script

my @finalnwlist = split (/\n/, join (' ', @networklist, @brnwlist, @vn
+wlist));


my @entries;
sub update_exports {

        my $exports = 'exports';
        open (EXPORTS,"<exports") ||die "Error opening exports file";
        my @lines = <EXPORTS>;
        close (EXPORTS);

        open (TMP_EXP, ">> exports_tmp") || die "File not found";

        foreach $a (@lines) {

            if ( $a =~ m/\*/) {
                logmsg "Generating unrestricted entry..";
                my ($share, $permission) = split (/\*/, $a);
                for my $b (@finalnwlist) {
                        @entries = join ('', $share, $b, $permission) 
+;
                        print TMP_EXP @entries;
                }
            }
            else {
                print TMP_EXP $a;
            }

        }
        close(TMP_EXP);
}
[download]