Lyrics from The Lester S. Levy Collection of Sheet Music:

(PACK UP YOUR TROUBLES IN YOUR OLD KIT BAG AND) SMILE, SMILE, SMILE!
Words, George Asaf. Music, Felix Powell. 1915.

Private Perks is a funny little codger with a smile, a funny smile.
Five feet none, he's an artful little dodger with a smile, a funny smile.
Flush or broke, he'll have his little joke. He can't be suppress'd.
All the other fellows have to grin when he gets this off his chest. Hi!

CHORUS: Pack up your troubles in your old kit-bag and smile, smile, smile.
While you've a lucifer to light your fag, smile, boys; that's the style.
What's the use of worrying? It never was worthwhile;
So pack up your troubles in your old kit-bag and smile, smile, smile.

Private Perks went a-marching into Flanders with his smile, his funny smile.
He was lov'd by the privates and commanders for his smile, his funny smile.
When a throng of Bosches came along with a mighty swing,
Perks yell'd out, "This little bunch is mine! Keep your heads down, boys, and sing. Hi!" CHORUS

Private Perks he came back from Bosche-shooting with his smile, his funny smile.
Round his home he then set about recruiting with his smile, his funny smile.
He told all his pals, the short, the tall, what a time he'd had;
And as each enlisted like a man, Private Perks said, "Now my lad, Hi!" CHORUS