This is Perl, so there's more than one way of doing this. One is indeed a regexp: 
$ext="i_am_the_walrus.txt";
$ext=~s/^[^.]*(\.[\w]+$)/$1/;
print $ext;

[download]
A second way is to use substr and index: 
use strict;
my $filename="you_are_the_whale.doc";
my $separator=".";
unless (($where=index($filename,$seperator) == -1) {
  my $ext=substr($filename,$where);
  print $ext;
} else {
  print "No extensions in the zoo.\n"; }

[download]
The third, and probably nicest way, is to use File::Basename: 
use strict;
use File::Basename;
my $filename="we_are_not_all_mammals.zoo";
my ($base, $directory, $ext)=fileparse($filename, '\.[\w]+$');
print $ext;

[download]
Beware that the above assumes you're dealing with simple .xyz extensions. For more complicated stuff, see the regexp in elusion's reply above.

CU
Robartes-

Update: Fixed regexp so it actually works :) (thx elusion). Adapted second recipe to include dot.

In reply to Re: Finding a extention by robartes
in thread Finding a extention by andrew

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.