Possible configuration.
\input TeX4ht.sty \Preamble{html} ... \EndPreamble \input ProTex.sty \AlProTex{extension,<<<>>>,list,title,escape-character}
The escape-character stands for `
, @
, |
, or ?
. If omitted, it stands for `\
'.
\<....\><<< ............ >>>
`<.....`>
\OutputCode\<...\>