I am having a problem with a regular expression on vim. I have a pattern as follows: http:\/\/\(\w\+\.\?\)\+ [matches http://(AS MANY WORDS FOLLOWED BY DOT OR NOT ENCOUNTERS) e.g. http://wd1.wd2.com] I have a text as follows: http://wd1.wd2.com/wd3 I am trying to make this substitution on it: s/\(http:\/\/\)\(\w\+\.\?\)\+/\1wd4.wd5.com and the result is http://wd4.wd5.com /wd3 (Notice the white space inserted at the end of the replacement) How can I avoid having this inserted space? I am afraid is a bug in the regexp engine but I am not sure.