Ideally, the function is POSIX-compatible, so it runs on the widest number of platforms.

Why do we want to adhere to POSIX?

  $ man bash | grep slow
         It's too big and too slow.

  $ rpm -qi dash | tail -3
  DASH is a POSIX-compliant implementation of /bin/sh that aims to be as small as
  possible. It does this without sacrificing speed where possible. In fact, it is
  significantly faster than bash (the GNU Bourne-Again SHell) for most tasks.

So let's find out how this function works in dash.

  $ ./testtrim
  ./testtrim

  $ sed -i 's/dash/bash/' testtrim          
  $ ./testtrim                              
  foo bar

I think I will pass.