How's this:

#!/usr/bin/perl -w

print "Content-type: text/html\n\n";

use strict;

my $version = "CMTS_V03.01.01.41, <<HW_REV: 1.3; VENDOR: ARRIS; BOOTR:
+ V00.01.0";

$version =~ s/^(.+)V([\d\.]+)$/$2/;

print $version,"\n";
[download]

But will be anxious to read the other ways.

Update: Abigail-II makes an interesting point, but I assumed that the version number, even if different, would appear in the same place (end of the string), with the "V" prefix. But I'm open...