<..html index target..>
\csname a:--\endcsname
-_-_-
<..html index source..>
\csname b:--\endcsname
-_-_-
<..indexes..>+
\NewConfigure{--}{2}
\Configure{--}
{\html:addr \Link-{}{<.idx htag.>\last:haddr}\EndLink}
{\string\csname\space :gobble\string\endcsname{\html:lbl}%
\string\Link[\FileName]{<.idx htag.>\last:haddr}{}\folio
\string\EndLink
}
-_-_-
The ‘\string\csname :gobble\string\endcsname{\html:lbl}%’ is for preserving source-ordering when identical key are present. We can’t put \:gobble explicitly because ‘:’ is loaded with cat code 12.