To help resolve your 2nd question about 2 processes...here is the general thought...
If 2 processes or more trying to access same file either you have to implement synchronization concept or threading concept means
one process should complete then only you have to allow other to get access to a file...because both processes needs
to access same file. find below some links which may shed you some idea on this... 
http://www.xav.com/perl/lib/Pod/perlthrtut.html
http://www.globalspin.com/thebook/chapter20.html
http://perldoc.perl.org/perlthrtut.html

[download]
Thanks & Regards
Sridhar

In reply to Re: File locking by mantra2006
in thread File locking by Nalina

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.