To make Vim show the hidden characters in the document you're editing, enter the command:
disable with
:help list
Quote:
*:l* *:list*
:[range]l[ist] [count] [flags]
Same as :print, but display unprintable characters with '^' and put $ after the line.
See |ex-flags| for [flags].
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:set invlist seems to do the same thing, but there's no help on that command....