The data in the reference file is as below. 
UTRIR8709990166-PRIS
UTRIR8709990166-IONJ
UTRIR8709990166-SONIC
UTRIR8709990166-INTR
UTRIR8709990166-MNSS
UTRIR8709990166-POIO
and so on

[download]

iam storing UTR (payment reference number) along with client seperated.
i will read the reference file containing above information, split and take UTR number into @sentUTRs array.
for information purpose , iam doing below..
recieve flat text file containing payments seperated by ~ in each line every 15 minutes
run this perl script and consider only new payments i.e. check reference file for already considered payments and ignore them and consider new payments and update these into reference file at the end.
All the new payments iam writing into CSV file w.r.t client.
so to achieve above, i just open flat file, read each line and split it and take second field containing UTR number and match it with the ones already sent in reference file and do further processing.

In reply to Re^2: Needed Performance improvement in reading and fetching from a file by Anonymous Monk
in thread Needed Performance improvement in reading and fetching from a file by harishnuti

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.