Currently, it is not possible to escape a literal period (.) to search for strings that contain a literal period. One use case is for searching documentation for "Mysql 4.x". All variations on escaping the period don't have any effect, the character is either stripped or interpreted as a single-character wildcard.
You can reproduce the problem by searching confluence.atlassian.com for "2.10" and then "2.*". The first returns documentation related to Confluence 2.10, the second returns anything with the number "2" in it.