iab <buffer> enum. \startitemize[n]<cr><cr>\stopitemize<up><tab>\item
iab <buffer> i. \item
Type the abbreviation (including the dot) followed by <tt>CTRL-]</tt></tt> to expand the snippet, then
continue typing normally.
Abbreviations may be triggered by any other non-keyword character (different from <tt><cCTRL-]></tt>),
but in that case such character is inserted in the text.