syn region factorString matchgroup=factorStringDelims start=/\v<"/ skip=/\v\\"/ end=/\v"/ contains=factorEscape
syn region factorString matchgroup=factorStringDelims start=/\v<"""/ skip=/\v\\"/ end=/\v"""/ contains=factorEscape
syn region factorString matchgroup=factorStringDelims start=/\v<[^[:blank:]"]+"/ skip=/\v\\"/ end=/\v"/ contains=factorEscape
syn region factorString matchgroup=factorStringDelims start=/\v<"/ skip=/\v\\"/ end=/\v"/ contains=factorEscape
syn region factorString matchgroup=factorStringDelims start=/\v<"""/ skip=/\v\\"/ end=/\v"""/ contains=factorEscape
syn region factorString matchgroup=factorStringDelims start=/\v<[^[:blank:]"]+"/ skip=/\v\\"/ end=/\v"/ contains=factorEscape