"Eric Haszlakiewicz" <erh+pgsql(at)swapsimple(dot)com> writes:
> I would expect this to return false:
> template1=# select 'xyz' ~ E'^(.)\\1*$';
> ?column?
> ----------
> t
> (1 row)
Seems to be a bug in the Tcl regexp library we use. It's already
reported upstream:
https://sourceforge.net/tracker/index.php?func=detail&aid=1115587&group_id=10894&atid=110894
regards, tom lane