You can use regular expressions (
http://dev.mysql.com/doc/refman/5.1/en/regexp.html), but obviously searches will not benefit from an index. If performance is an issue, and the ignored characters are all outside of A-Z, a-z, and 0-9, you might want to consider adding an additional indexed column that contains the filtered value (like TEMPA123), and searching on that column. The column could be populated when a record is added to the table.