Close -- it stands for both "vector" and/or "version" string. See Everything you wanted to know about Module Version Numbers and Checking for more while I hunt down something from the perl distribution which discussed them.

Update: Can't find anything about it in the core perl documentation, but there's a small bit about them in Programming Perl, version 3. A short exerpt from section 2.6.7 from my version on Safari:

A literal that begins with a v and is followed by one or more dot-separated integers is treated as a string literal composed of characters with the specified ordinal values:

$crlf = v13.10;           # ASCII carriage return, line feed

These are called v-strings, short for "vector strings" or "version strings" or anything else you can think of that starts with "v" and deals with lists of integers. They provide an alternate and more legible way to construct strings when you want to specify the numeric values of each character. Thus, v1.20.300.4000 is a more winsome way to produce the same string value as any of:

"\x{1}\x{14}\x{12c}\x{fa0}"
pack("U*", 1, 20, 300, 4000)
chr(1) . chr(20) . chr(300) . chr(4000)
[download]

perl -pe '"I lo*`+$^X$\"$]!$/"=~m%(.*)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'