$SEM = CREATE SEMAPHORE;
IF ($PID == FORK())
{
    wait($SEM); # grab the semaphore
    open file;    
    WRITE 'ALPHA';
    close file;
    signal($SEM); # signal semaphore
    wait($SEM); # wait for signal from child
    open file;
    WRITE 'BETA';
    close file;
    signal($SEM); # signal semaphore
}
ELSE IF(DEFINED $PID)
{
    SLEEP(3); # make sure parent grabs semaphore
    wait($SEM); # wait for signal from parent
    open file;
    READ THE FILE;
    close file;
    signal($SEM); # done with file ops, signal semaphore
    wait($SEM); # wait for signal from parent that it is done writing to file
    open file;
    READ THE FILE;
    close file;
    signal($SEM); 
}