collapseos/blk/204

Variable actions are expected to be called with labels in
front of them. Example, "L2 FSET"

About that "1 -": z80 relative jumps record "e-2", that is,
the offset that *counts the 2 bytes of the jump itself*.
Because we set the label *after* the jump OP1 itself, that's 1
byte that is taken care of. We still need to adjust by another
byte before writing the offset.