< chat > s/ foo / bar / is an idiom which means "I didn't mean to type 'foo', I meant to type 'bar'".
Its use in talk systems, especially irc , comes from the use of s/// as a substitution operator in Perl , sed and ed . In these languages and tools, s/foo/bar/ would replace any substring matching the regular expression "foo" with the string "bar".
(1997-03-16)