use Fcntl ':flock' ;
open ONE, ">> C:\\temp\\RTEOlock.log" or die $!;
my $lck = eval {flock ONE, LOCK_EX | LOCK_NB};
die 'flock not supported! ', $@ if $@;
if ($lck) {
    # The other script is not running code here
}
else {
    # The other script is running code here
}