Can't find documentation for ~=~ operator

Hi,

I can't find the documentation of the ~=~ operator anywhere on the
PostgreSQL homepage.  I'm quite certain that I saw it there a while ago,
though.

FYI, I use ~=~ for equality checks, so I can use the same index for
equality and regexp pattern matching on a varchar field.  The index is
built with varchar_pattern_ops.

Cheers,
Viktor