Try ipv4_checkip instead of ipv4check_ip.

ok now I am getting:

23.23.109.103
Use of inherited AUTOLOAD for non-method Net::IPv4Addr::ipv4_checkip()
+ is
        deprecated at number_test.pl line 15 (#1)
    (D deprecated) As an (ahem) accidental feature, AUTOLOAD subroutin
+es
    are looked up as methods (using the @ISA hierarchy) even when the
    subroutines to be autoloaded were called as plain functions (e.g.
    Foo::bar()), not as methods (e.g. < Foo-bar() >> or <
    $obj-bar() >>).
    
    This bug will be rectified in future by using method lookup only f
+or
    methods' AUTOLOADs.  However, there is a significant base of exist
+ing
    code that may be using the old behavior.  So, as an interim step, 
+Perl
    currently issues an optional warning when non-methods use inherite
+d
    AUTOLOADs.
    
    The simple rule is:  Inheritance will not work when autoloading
    non-methods.  The simple fix for old code is:  In any module that 
+used
    to depend on inheriting AUTOLOAD for non-methods from a base class
    named BaseClass, execute *AUTOLOAD = \&BaseClass::AUTOLOAD during
    startup.
    
    In code that currently says use AutoLoader; @ISA = qw(AutoLoader);
    you should remove AutoLoader from @ISA and change use AutoLoader; 
+to
    use AutoLoader 'AUTOLOAD';.
    
Can't locate auto/Net/IPv4Addr/ipv4_checki.al in @INC (@INC contains:
        /usr/local/lib /usr/local/lib/perl5/5.8.0/sun4-solaris /usr/lo
+cal/lib/perl5/5.8.0 
/usr/local/lib/perl5/5.8.0/sun4-solaris/CORE /usr/local/lib/perl5/site
+_perl/5.8.0/MIME /us
r/local/lib/perl5/5.8.0/CGI/ /usr/local/bin/perld/modules/Net-IPv4Addr
+-0.09/blib /usr/loca
l/lib/perl5/5.8.0/sun4-solaris /usr/local/lib/perl5/5.8.0 /usr/local/l
+ib/perl5/site_perl/5
.8.0/sun4-solaris /usr/local/lib/perl5/site_perl/5.8.0 /usr/local/lib/
+perl5/site_perl .) a
t number_test.pl line 15 (#2)
    (F) You said to do (or require, or use) a file that couldn't be
    found. Perl looks for the file in all the locations mentioned in @
+INC,
    unless the file name included the full path to the file.  Perhaps 
+you
    need to set the PERL5LIB or PERL5OPT environment variable to say w
+here
    the extra library is, or maybe the script needs to add the library
+ name
    to @INC.  Or maybe you just misspelled the name of the file.  See
    perlfunc/require and lib.
    
Uncaught exception from user code:
        Can't locate auto/Net/IPv4Addr/ipv4_checki.al in @INC (@INC co
+ntains: /usr/local/l
ib /usr/local/lib/perl5/5.8.0/sun4-solaris /usr/local/lib/perl5/5.8.0 
+/usr/local/lib/perl5
/5.8.0/sun4-solaris/CORE /usr/local/lib/perl5/site_perl/5.8.0/MIME /us
+r/local/lib/perl5/5.
8.0/CGI/ /usr/local/bin/perld/modules/Net-IPv4Addr-0.09/blib /usr/loca
+l/lib/perl5/5.8.0/su
n4-solaris /usr/local/lib/perl5/5.8.0 /usr/local/lib/perl5/site_perl/5
+.8.0/sun4-solaris /u
sr/local/lib/perl5/site_perl/5.8.0 /usr/local/lib/perl5/site_perl .) a
+t number_test.pl lin
e 15
        AutoLoader::AUTOLOAD(23.23.109.103) called at number_test.pl l
+ine 15
[download]

My PERL5LIB path is

/usr/local/lib:/usr/local/lib/perl5/5.8.0:/usr/local/lib/perl5/5.8.0/s
+un4-solaris/CORE:/us
r/local/lib/perl5/site_perl/5.8.0/MIME:/usr/local/lib/perl5/5.8.0/CGI/
+:/usr/local/bin/perl
d/modules/Net-IPv4Addr-0.09/blib
[download]

2004-12-04 Janitored by Arunbear - added code tags, as per Monastery guidelines

Ah, the POD lies. It's ipv4_chkip. Your code works for me with this change.

Hi there:

Of course I am biased, but how about... (untested)

use strict;
use warnings;

use vars qw($is_this_an_IP_address); 
use NetAddr::IP;

my $ip = new NetAddr::IP $is_this_an_IP_address;

if ($ip)
{
  # This is a valid IP address, or something an IP address can be deri
+ved
  # from
}
else
{
  # This is not an IP address
}
[download]

I went to report the doc error, and found a major, easy-to-fix bug that's been ignored for two years. ipv4_chkip will pass any string of four or more integers between 0 and 255 connected by .'s. The deal-breaker here is the 'four or more' instead of 'exactly four.'

So I can't recommend it. Perhaps try Regexp::Common instead.

use Net::IPv4Addr qw(:all);
use Regexp::Common qw(net);

my @var = qw(23.23.109.103 12324.123.12.1 1.2.3.4.5.6);

print "Net::IFv4Addr:\n";
ipv4_chkip($_) and print "$_ is good\n" for @var;
print "Regexp::Common:\n";
/^$RE{net}{IPv4}$/ and print "$_ is good\n" for @var;
[download]

produces

Net::IFv4Addr:
23.23.109.103 is good
1.2.3.4.5.6 is good
Regexp::Common:
23.23.109.103 is good
[download]

Note that you do need to anchor the start and end of the regexp with ^ and $, 'cause just /$RE{net}{IPv4}/ would match 312.45.32.4.