Harel statemachine for Lua 5.4

I have problems getting package `hsm_statechart` working under Lua 5.4 (which should support > Lua 5.1). After `luarocks install hsm_statechart`, when I load the package it says `luaL_register undefined` which tells me it​'s not updated for Lua 5.4... I've downloaded the source and tried to update it, but not successful so far. Anyone using hsm_statechart under Lua 5.4 (I'm aware of other statecharts but they are pure lua code and may be slower than the C-compiled hsm_statechart module).

Thanks.