〜ものを

早(はや)く言(い)えばよかったものを。

Hayaku ieba yokatta mono o.

If only you had said so sooner.

ものを is if only, carrying regret and reproach

相談(そうだん)してくれれば助(たす)けたものを。

Sōdan shite kurereba tasuketa mono o.

Had you asked me, I would have helped.

It often ends the sentence there, trailing off

文学(ぶんがく)と芝居(しばい)の言い回(いいまわ)しです。

Bungaku to shibai no iimawashi desu.

It is the phrasing of literature and the stage.

Modern speech uses のに