tcl-yajltcl binary package in Ubuntu Focal armhf

 yajl-tcl, a Tcl C extension written to bring the capabilities
 of the Yet Another JSON Library (YAJL), a C library for parsing
 and generating JSON, available to Tcl coders. JSON stands for
 Javascript Object Notation, a popular data exchange format for
 Javascript.
 .
 Although there is already a package in the tcllib library,
 that can generate JSON, the big advantage in using yajl-tcl
 is performance. Also, yajl-tcl can parse JSON as well as
 generating it.

Source package