He published more than fifty collections of poetry, a few of them in cooperation with some other Danish poets, namely Asger Schnack and Klaus Høeck.
[6] Jac often utilised autobiographical material in his writing, generously twisting everything to an innovative, kind-hearted, humorous and above all distinct voice.
Approaching everyday life with a defiant ability to find beauty and oddness he coined many new words describing feelings and situations previously unaccounted for in Danish.
This gave him a reputation for being an eccentric with a slanted and highly personal use of language, but also brought him much acclaim among peers and a large fan base.
In 2008, 1 month before his death, he was thus awarded the grand prize of the Academy for the Arts for his life achievement in regards to kindling the Danish language.