Well, as long as we are providing a more complete reference, here's:
Shorthand Character Classes at regular-expressions.info
Perl 5.10 introduced \h and \v. \h matches horizontal whitespace, which includes the tab and all characters in the "space separator" Unicode category. It is the same as [\t\p{Zs}]. \v matches "vertical whitespace", which includes all characters treated as line breaks in the Unicode standard. It is the same as [\n\cK\f\r\x85\x{2028}\x{2029}].
PCRE also supports \h and \v starting with version 7.2. PHP does as of version 5.2.2, Java as of version 8, and the JGsoft engine as of version 2. Boost supports \h starting with version 1.42. No version of Boost supports \v as a shorthand.
In many other regex flavors, \v matches only the vertical tab character. Perl, PCRE, and PHP never supported this, so they were free to give \v a different meaning. Java 4 to 7 and JGsoft V1 did use \v to match only the vertical tab. Java 8 and JGsoft V2 changed the meaning of this token anyway. The vertical tab is also a vertical whitespace character. To avoid confusion, the above paragraph uses \cK to represent the vertical tab.
Ruby 1.9 and later have their own version of \h. It matches a single hexadecimal digit just like [0-9a-fA-F]. \v is a vertical tab in Ruby.
That's one reason I always test my RegEx patterns at RegEx101.com. They provide a language selector:
Although this says "pcre (php)" I believe pcre stands for Perl Compatible Regular Expressions. The ICU RegEx used by KM is based on perl RegEx, so I use the RegEx101.com "pcre" for KM testing.
Finally here's wikipedia's take:
Comparison of regular expression engines