Locals created outside fl() are not accessible from within:
lv(a, 1) + fl(0,0,0, "#a") => #a
However locals created inside fl() are accessible from outside:
fl(0,0,0, "lv(b, 1)") + #b => 1
Workaround for now - append setting locals to fl() body:
lv(a, 1) + fl(0,0,0, "lv(a, "+#a+") + #a")
If your local is a string that might contain characters that can’t be in quoteless strings, you can use this trick to wrap it in quotes by using ' as a placeholder:
lv(a, 1) + fl(0,0,0, tc(reg, "lv(a, '"+#a+"') + #a", ', tc(utf, 22)))