There are 10,000 ways to do something like this in perl... Here is a simple snippet that will modfiy a line in an array and then write it to an output file.
$filein=yourcvsfile.txt;
$fileout=yourcvsfileout.txt;
####read into array
open (FILEIN,"$filein") || die "Can't Open  file : $!\n";
@mydata=<FILEIN>;
close FILEIN;
####open output file
open (FILEOUT,">$fileout") || die "1Can't Open b: $!\n";


foreach $mydata (@mydata) {($newfield1,$newfield2,$newfield3,$newfield
+4,$newfield5) = split(',',$newline);

if ($newfield1 eq $newvar)
 {$field1=$var1;
###preform sub routine to write
&writenew};

sub writenew {
$newfield1=$var2;
$newfield2=$var2
$newfield3=$var2
$newfield4=$var2
$newfield5="anydata";
$mydata="$newfield1,$newfield2,$newfield3,$newfield4,$newfield5; "
print FILEOUT $mydata;

}

[download]
This may not be exact but it will give you a start--hopefully!!--

In reply to Re: Adding a field into CSV and populating by erniep
in thread Adding a field into CSV and populating by nickjwest

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.