This is a vi syntax highlighting trick gmax emailed to me. It changes the syntax highlighting for here documents and the qq() and q() operators as long as braces {} are used to delimit them (that is the trick, you see). This example 'embeds' the MySQL highlighting scheme inside Perl code. Example.

Find the perl.vim file that is being used by your version of vi, usually somewhere in /usr/share/vim/

Add this syntax to it:

syn include @Sql <sfile>:p:h/mysql.vim
syn region perlSQL start="qq{" end="}" contains=@Sql keepend
syn region perlSQL start="q{"  end="}" contains=@Sql keepend
syn region perlSQL start="<<MYSQL" end="^MYSQL" contains=@Sql keepend

let b:current_syntax = "perl"

and save this file [mysql.vim] to the same directory as the file you just edited (perl.vim).