Hi, Monetdb is using pcre library for regular expression support, and using this function we can allow SQL to use the regex library: CREATE FUNCTION "pcre_replace" (origin string, pat string, repl string,flags string) RETURNS string EXTERNAL NAME pcre."replace"; I want to use regex for date conversion to the format supported by monetdb (yyyy-MM-dd), I have the following format dd/MM/yyyy, and i am trying to run the following with no success: select pcre_replace('15/10/2015', '^(3[01]|[12][0-9]|0?[1-9])/(1[012]|0?[1-9])/([0-9]{4})$', '\\3-\\2-\\1', 'i') select pcre_replace('15/10/2015', '^(3[01]|[12][0-9]|0?[1-9])/(1[012]|0?[1-9])/([0-9]{4})$', '{3}-{2}-{1}', 'i') select pcre_replace('15/10/2015', '^(?<day>3[01]|[12][0-9]|0?[1-9])/(?<month>1[012]|0?[1-9])/(?<year>[0-9]{4})$', '\\k<year>-\\k<month>-\\k<day>', 'i') My question is, is backreference supported in the replacement string; if yes, whats is the right syntax to use to reference the detected groups, if no, is there a clever way then using substring? Thanks