expression
it is regrettable that ...; it's a pity that ...; unfortunately, ...
A formal, somewhat literary expression used to introduce a statement of regret or disappointment. Often found in written Japanese or formal speech.
惜しむらくは、彼の才能が十分に生かされなかったことだ。
It is regrettable that his talent was not fully utilized.
惜しむらく
Unfortunately, the weather didn't cooperate, and we couldn't enjoy the scenery we had come for.