"Please do not borrow my dictionary."
The verb is かりる, not かる. Basically it's a godan verb like たべる or みる where you just cut off the る at end for conjugation rather than change it to a ら。It's somewhat confusing and nuanced, and I believe if you're at all interested in the grammar of the language, I'd do research on it
In classical japanese it was the verb 借る (かる) indeed, but evolved to 借りる (かりる) in modern langugage and therefore become an ichidan verb (一段動詞).
So it's ren'youkei (or so called masu-stem) is just dropping the last る instead of inflecting to り (like would be done with the classic form).
As I understand it keeps it original form only in some dialects
or in old idioms like 虎の威を借る狐 (A fox that borrows the authority of a tiger).