Green’s Dictionary of Slang

purl v.

[SE purl, often of a top, to spin round and round; an earlier version was pirl]

to turn upside down, to overturn, to upset, to turn a somersault.

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[UK]Era (London) 28 July 7/4: Callaghan [...] administered [...] a bouncing hit on the ribs, which made Oakley purl again.
[UK]C. Reade It Is Never Too Late to Mend II 170: They commonly paddle in companies of three; so then whenever one is purled the other two come on each side of him, each takes a hand with amazing skill and delicacy they reseat him in his cocked hat, which never sinks – only purls.