I usually do this:

my $IP = ENV('REMOTE_ADDR', '0.0.0.0');

print $IP;
exit;

###################
# This function returns an environment variable named in the
# first argument. If the environment variable doesn't exist,
# then DEFAULT is returned. However, if a third argument is
# given, then that will be returned in every case.
# The third argument is used for tweaking and testing purposes.
#
# Usage: VALUE = ENV( NAME, [DEFAULT, [OVERRIDE]] )
#

sub ENV
{
  return '' unless @_;     # No arguments at all?
  my $NAME = shift;                # Get NAME
  my $DEFAULT = @_ ? shift : '';   # Get DEFAULT value
  return shift if @_;              # OVERRIDE?
  return $DEFAULT unless defined $NAME;  # NAME undefined?
  return $DEFAULT unless $NAME;          # NAME is blank?
  if (exists($ENV{$NAME})) { return Trim($ENV{$NAME}); }
  return $DEFAULT;
}

###################
#
# This function removes whitespace before and after STRING
# and returns a new string.
#
# Usage: STRING = Trim(STRING)
#
sub Trim
{
  return '' unless @_;
  my $T = shift;
  return '' unless defined $T;
  return '' unless length($T);

  my $s = -1;   # start ptr
  my $e = 0;    # end ptr
  for (my $i = 0; $i < length($T); $i++)
  {
    if (vec($T, $i, 8) > 32)
    {
      if ($s < 0) { $s = $i; }
      $e = $i;
    }
  }
  return substr($T, $s, $e - $s + 1);
}
[download]

This means, even if REMOTE_ADDR is undefined for whatever reason, I get a string in $IP which is going to be 0.0.0.0. And then I know that it's because it was undefined!

---

---

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! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

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:
	&		&
	<		&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.