How to match up to a word

[jjaso...@gmail.com]

I'm writing a program that processes a log file. I need to search for
everything up to a single word. I'm currently doing it with a positive
look ahead but I'm not sure if this is the most efficient way to do it.
Anyone have any ideas on how to improve this?

Ex. string - blah blah foo bar blah end
currently use - ^([\w ]+)(?=end)end

Thanks,
Jason