Definition of "alas"

Helas I lamente the dull abuſyd brayneThe enfatuate fantaſies the wytles wylfulnesOf on and hothyr at me that haue dyſdayne

c. 1521, John Skelton, Speke Parott

Alas poore Yorick, I knew him Horatio, a fellow of infinite Ieſt; of moſt excellent fancy, he hath borne me on his backe a thouſand times: And how abhorred my Imagination is, my gorge riſes at it.

c. 1599–1602 (date written), William Shakespeare, “The Tragedie of Hamlet, Prince of Denmarke”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act V, scene i], page 278, column 1

The thorough and shameless commercialism of Sex has alas! been reserved for what is called "Christian civilization," and with it (perhaps as a necessary consequence) Prostitution and Syphilis have grown into appalling evils, accompanied by a gigantic degradation of social standards, and upgrowth of petty Philistinism and niaiserie.

1920, Edward Carpenter, Pagan and Christian Creeds, New York: Harcourt, Brace and Co., published 1921, page 188