There are few lines where I don't agree:

my $column_separator = ",";

[download]
Better: 
my $column_separator = qr/,/;

[download]
...imaging someone wants to use "." as separator. 

my $column_number = "3";

[download]
Don't write numbers as text, write them as numbers (cut away those " chars).

Loading the whole file into memory might not be that good idea, imagine it's a 10 GB file. Why not parse it line-by-line?

open(FILE,"<","$file");
while (<FILE>) {
 my @columns = split(/$column_separator/);
 print $columns[$column_number],"\n";
}
close FILE;

[download]

Try out Padre - the free Perl IDE and visit my blog's Perl section.

In reply to Re^2: extracting single column by Sewi
in thread extracting single column by Anonymous Monk

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.