A Google search yielded a slightly larger fragment than you have, at this site.

"A great man with the knife is the Bulgar. Did you ever hear that
song about him they sang at a revue the British 'Tommies' had at
Saloniki? It was a parody on some other song that was being sung in the
halls in London, and went something like this:

[Sidenote: A Bulgar song.]

I'm Boris the Bulgar,
The Man With the Knife;
The Pride of Sofia,
The Taker of Life.
Good gracious, how spacious
And deep are the cuts,
Of Boris the Bulgar,
The Knifer--"