Kaloyan Iliev Iliev <news1(at)faith(dot)digsys(dot)bg> writes:
> libvar=# select '\\a\\\\\\.' ~ '\\a\\\\\\.';
> ERROR: invalid regular expression: invalid escape \ sequence
7.4 and later are stricter about the use of \ than prior versions; see
http://www.postgresql.org/docs/7.4/static/functions-matching.html#POSIX-ESCAPE-SEQUENCES
You could go back to (approximately) the old behavior by changing
regex_flavor to "extended".
regards, tom lane