$SET_FIELD="first_child|next_sibling|pcdata|cdata|ent|data|target|comment|flushed";
s{(\$[a-z_]+(?:\[\d\])?)             # $1: the object
   ->set_($SET_FIELD)                # $2: the field to set
   \(([^)]*)\)}                      # $3: the value (must not include ())
 {$1\->\{$2\}= $3}gx;