use Fcntl qw(:DEFAULT :flock);

sysopen(FILE, "$datapath/members/carts/$FORM{'username'}.txt", O_RDWR) or die "Can't open: $!";
flock(FILE, LOCK_EX);

$ItemIndex = "$FORM{'item'}|$FORM{'num'}|$FORM{'price'}|$FORM{'desc'}|$FORM{'quant'}|";

@FileContents = <FILE>;
@DeletedItem = splice(@FileContents, $ItemIndex, 1);

seek(FILE, 0, 0) or die "Can't return to beginning: $!";
truncate(FILE, 0) or die "Can't truncate file to zero length: $!";
print FILE @DeletedItem;

flock(FILE, LOCK_UN);
close(FILE);

open(OLDFILE, "<$datapath/members/carts/$FORM{'username'}.txt") or die "Can't open: $!";
@old_file = <OLDFILE>;
@new_file = grep { !/^$FORM{'item'}|$FORM{'num'}|$FORM{'price'}|$FORM{'desc'}|$FORM{'quant'}|/ } @old_file;
close(OLDFILE);
open(FILE, ">$datapath/members/carts/$FORM{'username'}.txt") or die "Can't open: $!";

print FILE @new_file; # Write the new data into the file.

close(FILE);