makeprg=make\\,file	    results in "make\,file"
   :set tags=tags,file		    results in "tags" and "file"
   :set tags=tags\\,file	    results in "tags\,file"
   :let &tags='tags\,file'	    (same as above)

The "|" character separates a ":set" command from a following command.  To
include the "|" in the option value, use "\|" instead.  This example sets the
'titlestring' option to "hi|there": >
   :set titlestring=hi\|there
This sets the 'titlestring' option to "hi" and 'iconstring' to "there": >
   :set titlestring=hi|set iconstring=there

Similarly, the double quote character starts a comment.  To include the '"' in
the option value, use '\"' instead.  This example sets the 'titlestring'
option to "hi "there"": >
   :set titlestring=hi\ \"there\"

For Win32 backslashes in file names are mostly not removed.  More precise: For
options that expect a file name (those where environment variables are
expanded) a backslash before a normal file name character is not removed.  But
a backslash before a special character (space, backslash, comma, etc.) is used
like explained above.
There is one special situation, when the value starts with "\\": >
   :set dir=\\machine\path	    results in "\\machine\path"
   :set dir=\\\\machine\\path	    results in "\\machine\path"
   :set dir=\\path\\file	    results in "\\path\file" (wrong!)
For the first one the start is kept, but for the second one the backslashes
are halved.  This makes sure it works both when you expect backslashes to be
halved and when you expect the backslashes to be kept.  The third gives a
result which is probably not what you want.  Avoid it.

				*add-option-flags* *remove-option-flags*
				*E539*
Some options are a list of flags.  When you want to add a flag to such an
option, without changing the existing ones, you can do it like this: >
   :set guioptions+=a
Remove a flag from an option like this: >
   :set guioptions-=a
This removes the 'a' flag from 'guioptions'.
Note that you should add or remove one flag at a time.  If 'guioptions' has
the value "ab", using "set guioptions-=ba" won't work, because the string "ba"
doesn't appear.

			   *:set_env* *expand-env* *expand-environment-var*
Environment variables in specific string options will be expanded.  If the
environment variable exists the '$' and the following environment variable
name is replaced with its value.  If it does not exist the '$' and the name
are not modified.  Any non-id character (not a letter, digit or '_') may
follow the environment variable name.  That character and what follows is
appended to the value of the environment variable.  Examples: >
   :set term=$TERM.new
   :set path=/usr/$INCLUDE,$HOME/include,.
When adding or removing a string from an option with ":set opt-=val" or ":set
opt+=val" the expansion is done before the adding or removing.


Handling of local options			*local-options*

Note: The following also applies to |global-local| options.

Some of the options only apply to a window or buffer.  Each window or buffer
has its own copy of this option, thus each can have its own value.  This
allows you to set 'list' in one window but not in another.  And set
'shiftwidth' to 3 in one buffer and 4 in another.

The following explains what happens to these local options in specific
situations.  You don't really need to know all of this, since Vim mostly uses
the option values you would expect.  Unfortunately, doing what the user
expects is a bit complicated...

When splitting a window, the local options are copied to the new window.  Thus
right after the split the contents of the two windows look the same.

When editing a new buffer, its local option values must be initialized.  Since
the local options of the current buffer might be specifically for that buffer,
these are not used.  Instead, for each buffer-local option there also is a
global value, which is used for new buffers.  With ":set" both the local and
global value is changed.  With "setlocal" only the local value is changed,
thus this