Are brang and brung examples of errors in a English?

Yes, "brang" and "brung" are considered nonstandard forms of the past tense and past participle of the verb "bring". The correct forms are brought for both tenses.

* Past Tense: "I brought my lunch to school today."

* Past Participle: "I have brought you a gift."

"Brang" and "brung" are often used in regional dialects or by speakers who are not fully fluent in standard English. They are considered grammatical errors in formal writing and speech.