in reply to Writing to a file which is external to cgi-bin directory

You forgot to open OUT.

And please use constants instead of magical numbers. Replace 

seek(OUT, 0, 2);

[download]
with 
use Fcntl qw( SEEK_END );
seek(OUT, 0, SEEK_END);

[download]

Update: Added the comment about using meaningful constants.

In Section Seekers of Perl Wisdom