Add $replace Modifier Operation

MongoDB is missing a $replace operator to perform search/replace operations on strings. MongoDB cannot currently perform the equivalent of the below SQL statement without updating each item individually:

UPDATE table SET column1 = REPLACE(column1, 'search', 'replace');

The modifier operator I propose would look like this:

db.coll.update(

, {$replace: {myprop: ["foo", "bar"]}});

The above statement would find all of the documents whose "a" property is 1, and replace "foo" with "bar" in the "myprop" property of said documents. A patch is attached that demonstrates this functionality. The operator should eventually support regular expressions and maybe even arrays, e.g.:

db.coll.update(

, {$replace: {myprop: [/foo\d+/, "bar"]}});

The above would replace all instances of "foo", followed by one or more digits, with the string "bar".