The past tense and past participle of the verbs learn, spoil, spell, burn, dream, smell, spill, leap, and others, can be either irregular (learnt, spoilt, etc.) or regular (learned, spoiled, etc.). In BrE, both irregular and regular forms are current, but for some words (such as smelt and leapt) there is a strong tendency towards the irregular forms, especially by users of Received Pronunciation. For other words (such as dreamed, leaned, and learned) the regular forms are somewhat more common. In most accents of AmE, the irregular forms are never or rarely used (except for burnt, leapt and dreamt).
The t endings may be encountered frequently in older American texts, especially poetry. Usage may vary when the past participles are used as adjectives, as in burnt toast. (The two-syllable form learnèd /ˈlɜrnɪd/, usually written without the accent, is used as an adjective to mean "educated" or to refer to academic institutions in both BrE and AmE.) Finally, the past tense and past participle of dwell and kneel are more commonly dwelt and knelt in both standards, with dwelled and kneeled as common variants in the US but not in the UK.