Regular expression is the wrong approach IMHO. The IPv4 address consists of four bytes (0..255) separated by dots.
Have a loock at split and pack. If you pack the byte values and unpack them again and assemble the IP string, origin and result should be equal if the origin is a valid IP address. 

print "Enter IP Address:";
chop(my $ip = <STDIN>);
my $parsed = join'.', unpack "C4", pack "C4", split/\./, $ip;
if ($parsed eq $ip) {
    print "yes match $parsed\n";
} else {
    print "no match: parsed $parsed <> input $ip\n";
}

[download]

This of course doesn't work for IP addresses written with leading zeroes e.g 001.012.013.225 - which I consider bad practice anyways, because in my book a leading zero marks an octal value.

If you want to be absolutely sure, you can isolate the four bytes with a regular expression limiting each string representation to 3 chars of type number, i.e (\d{3]), then run the four values through pack/unpack as described above. There are many other ways to do this task...

perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'

In reply to Re: Validate Ip address Regexp by shmem
in thread Validate Ip address Regexp by akr8986

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.