syn region factorMethodDelims start=/\v<M:>/ skip=/\v<!>.*/ end=/\v<\S+%(\_\s+%(!>.*)?)+\S+>/ contains=@factorComment skipempty keepend contained
syn region factorLocalsMethod start=/\v<M::>/ matchgroup=factorLocalsMethodDelims end=/\v<;>/ contains=factorLocalsMethodDelims,@factorCluster
syn region factorLocalsMethodDelims start=/\v<M::>/ skip=/\v<!>.*/ end=/\v<\S+%(\_\s+%(!>.*)?)+\S+>/ contains=@factorComment nextgroup=factorStackEffectSkip skipempty keepend contained
syn region factorMethodDelims start=/\v<M:>/ skip=/\v<!>.*/ end=/\v<\S+%(\_\s+%(!>.*)?)+\S+>/ contains=@factorComment skipempty keepend contained
syn region factorLocalsMethod start=/\v<M::>/ matchgroup=factorLocalsMethodDelims end=/\v<;>/ contains=factorLocalsMethodDelims,@factorCluster
syn region factorLocalsMethodDelims start=/\v<M::>/ skip=/\v<!>.*/ end=/\v<\S+%(\_\s+%(!>.*)?)+\S+>/ contains=@factorComment nextgroup=factorStackEffectSkip skipempty keepend contained