Regex question...

In my never-ending battle against swearing on my site, I'm trying to use a regex that changes any word that ends with abc to xyz. I'm using: $tofilter = "This is a string containing the word 123abc."; $tofilter= eregi_replace("[^ ]abc","xyz",$tofilter); But it returns "12xyz". It clearly picks up "3abc" before "123abc". I've also tried two regexes that check for it as a seperate word and at the begining of the string using $tofilter = "This is a string containing the word 123abc."; $tofilter= eregi_replace(" [^ ]abc","xyz",$tofilter); $tofilter= eregi_replace("^[^ ]abc","xyz",$tofilter); But that doesn't work at all. Any ideas on how to do this? -- The above message is encrypted with double rot13 encoding. Any unauthorized attempt to decrypt it will be prosecuted to the full extent of the law.