in emacs, append-next-kill sometimes prepends

Question

For example, place point at the beginning of a line with the text "foo bar". Then M-d C- C-e M-C-w C-w C-y produces " barfoo". This behaviour causes problems when I try to switch the order of text and when I combine a real kill with save-as-kill. No doubt prepending is often useful, but all the documentation I have found says that append-next-kill appends. How do I control emacs's choice between appending and prepending?

Answer 1

See the Emacs manual, node Appending Kills. It gives explicit examples, in particular an example that shows clearly what C-M-w is for and what it does. Here is part of that text:

If a kill command is separated from the last kill command by other
commands (not just numeric arguments), it starts a new entry on the kill
ring.  But you can force it to append by first typing the command
`C-M-w' (`append-next-kill') right before it.  The `C-M-w' tells the
following command, if it is a kill command, to append the text it kills
to the last killed text, instead of starting a new entry.  With
`C-M-w', you can kill several separated pieces of text and accumulate
them to be yanked back in one place.

For C-M-w to append the next kill, that kill must immediately follow C-M-w. If you do something else in between then there is no appending. The command name might better have been append-next-kill-if-it-follows-immediately. ;-)