I use sysopen when I want my scripts to play nicely with each other, and observe locking. eg:

use Fcntl qw(:DEFAULT :flock);

sysopen(OUT, $file, O_WRONLY | O_CREAT)
   or die "Cannot open $file for writing:$!\n";
flock(OUT, LOCK_EX)
   or die "Cannot get a lock on $file:$!\n";
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(That example is pretty much straight out of the book)

Cheers,
Darren :)