Is learning another procedural/OO language really that tough? I've put off learning Haskell/Erlang/etc because it's such a shift in thinking, but PHP/Ruby/Pytho

Is learning another procedural/OO language really that tough? I've put off learning Haskell/Erlang/etc because it's such a shift in thinking, but PHP/Ruby/Python/Java/JS/C-whatever seem to all be about the same. There's some new syntax, and entire new libraries, but it just means you have have the docs open a bunch at first. I find I have to actively _keep_ myself from starting new projects in the new flavor of the month and force myself to use something that I know much better and that is much more proven. I think I'd be rather proud of myself if I got a whole project done in PHP rather than Node or Scala or JRuby or something like that.