another with delta timer

const SPEED=-220
const SHOOT_INTERVAL=1
var shoot_timeout=0

func _process(delta):
	translate( Vector2(SPEED*delta,0) )
	shoot_timeout-=delta

	if (shoot_timeout<0):

		shoot_timeout=SHOOT_INTERVAL

		#instance a shot
		var shot = preload("res://enemy_shot.scn").instance()
		#set pos as "shoot_from" Position2D node
		shot.set_pos( get_node("shoot_from").get_global_pos() )
		#add it to parent, so it has world coordinates
		get_parent().add_child(shot)

var destroyed=false