QGIS/resources/function_help/json/regexp_replace

{
  "function": "regexp_replace",
  "description": "Returns a string with the supplied regular expression replaced.",
  "arguments": [ {"arg":"input_string","description":"the string to replace matches in"},
  {"arg":"regex","description":"The regular expression to replace. Backslash characters must be double escaped (eg \"\\\\s\" to match a white space character). Non-greedy regular expressions are not supported."},
  {"arg":"replacement","description":"The string that will replace any matching occurrences of the supplied regular expression. Captured groups can be inserted into the replacement string using \\\\1, \\\\2, etc."}
  ],
  "examples": [ { "expression":"regexp_replace('QGIS SHOULD ROCK','\\\\sSHOULD\\\\s',' DOES ')", "returns":"'QGIS DOES ROCK'"}]
}