in reply to Re: Using read/write to update a file
in thread Using read/write to update a file

I believe that you will end up overwriting the next record, not appending. So if you start with a file 

afoo
bfoo
cfoo
dfoo

[download]
you should end up with 
afoo
abar
cfoo
cbar

[download]

(untested)

--MidLifeXis

In Section Seekers of Perl Wisdom