Make sure 'ignorecase' is off:
:set noignorecase
:%s/\<[a-z]\+\>//g
If you don't want to bung with your vim-wide (or bufferwide)
settings, you can always just change your :s to include the "I" flag.
:%s/\<[a-z]\+\>//gI
Additionally, this will not find "camel-case" words, such as
strFooBarBaz (which can be common if your source text is code)
To accomodate that, you can use
:%s/\<\l\w*\>//gI
(that is "backslash ell" not "backslash one", which is a slightly
shorter notation for "[a-z]", and may have some unicode plusses
to it)
You can learn more at
:help :s_flags (and scroll down to the "I")
:help /\l
:help /\w
to tailor the regexp for exactly what you're hunting.
-tim
