Would that I were young again.是什么意思？

Would that I were young again.

我若能返老还童该多好。

would

aux. 将，将要，愿意，会，打算，大概；v. (will 的过去式，用于转述)将；

例句
I would love to go abroad this year, perhaps to the South of France.
我今年很想出国，可能是去法国南部。

that

det. 那个，那；pron. 那个，那；conj. 多么，如此…以至，用于某些动词、形容词和名词后，引出各种从句；adv. 不那么，那样；

例句
...expensive make-up that we saw being advertised by a beautiful model...
我们所见的由一位漂亮模特代言的昂贵化妆品

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

young

adj. 年幼的，有朝气的，年轻人的，青年的；n. 年轻人，幼小的动物，崽；

例句
...incentives to private landlords to accept young people as tenants.
鼓励私人房东租房给年轻人的措施

again

adv. 再一次，再说，此外，不过；

例句
It's easier to take a taxi. But then again you can't always get one...
打出租车要容易些，但也并不总是能打到的。