Green’s Dictionary of Slang

(US campus) a pfx indicating permanence, continuity.

1981		Eble Campus Sl. Mar. 5: perma [...] ‘After four beers he had a perma-grin.’.
1996		Eble Sl. and Sociability 32: Perma-, a shortening of permanent [...] inspires permagrin (‘After just two beers she had permagrin’), permagross, permanerve, and permaproblem.