Ruby HEREDOC highlighting

ruby-heredoc-highlighting

let s:bcs = b:current_syntax
unlet b:current_syntax
syntax include @SQL syntax/sql.vim

" this unlet instruction is needed
" before we load each new syntax
unlet b:current_syntax
syntax include @SHELL syntax/sh.vim

let b:current_syntax = s:bcs

syntax region hereDocText    matchgroup=Statement start=+<<[-~.]*\z([A-Z]\+\)+ end=+^\s*\z1+ contains=NONE

syntax region hereDocDashSQL matchgroup=Statement start=+<<[-~.]*\z(SQLDOC\)+  end=+^\s*\z1+ contains=@SQL

syntax region hereDocDashShell matchgroup=Statement start=+<<[-~.]*\z(SHELLDOC\)+  end=+^\s*\z1+ contains=@SHELL