Perl-ish Extended Regexes

" Perlish extended regexs
" Barry Arthur, Sep 2011

function! R(s)
  return substitute(substitute(a:s, '".\{-}\s\+_', '', 'g'), '\s\+', '', 'g')
endfunction

function! TestThis(str)
  let my_extended_regex = '
        \ ^     " start of line    _
        \ \s*   " skip whitespace  _
        \ \w\+  " first word       _
        \'
  return matchstr(a:str, R(my_extended_regex))
endfunction

echo TestThis("hello, world")