use warnings;
use strict;

use File::Touch;

my $lock = '/var/memdir/script.lock';

exit if -e $lock;

touch($lock); # dies on error by default

printf "Exists after create: %d\n", -e $lock // 0;

# do stuff

unlink $lock or die "Can't delete the damned lock file $lock: $!";

printf "Exists after delete: %d\n", -e $lock // 0;