Well, so far two VERY contradictory answers. What to do?

Believe them both. The typical web user is not forging or altering their HTTP headers, although in some cases the information may not be terribly useful. But anyone who wants to can easily insert just about any value they like into those fields (potentially even values that pose security threats-- so remember to use taint for added safety). To get a list of every value available to you in a CGI (which will depend on which browser you run this test with), you can run a little script like: 
#!/usr/bin/perl -wT
use strict;

my $CGI = new CGI;

print( $CGI->header(),
       $CGI->start_html( -title => 'Save the Environment' ),
       $CGI->h1( 'Here are the $ENV variables I see' )
      );
print $CGI->p( "$_ = $ENV{$_}" ) for ( keys %ENV );
print $CGI->end_html();

[download]
(please note the code above is untested).

In reply to (ichimunki) Re: How can I get useful info from $user = $ENV{'REMOTE_ADDR'}; by ichimunki
in thread How can I get useful info from $user = $ENV{'REMOTE_ADDR'}; by jerrygarciuh

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.