use vars qw($LF);

sub new
{
        my $proto = shift;
        my $class = ref($proto) || $proto;

        open(FH, ">".LOCK_FILE) or die "ERROR: cannot open lock file: ".LOCK_FILE.": $!\n";

        my $this = {
                LF => \*FH
        };

        bless($this, $class);

        return $this;
}
....

#
# code_lock()
# Lock a section of code.
#

sub code_lock
{
        my $this = attr shift;

        my $ret = flock $LF, LOCK_EX;
        return scalar $ret;
}