There is always going to be a lookup, its just a matter of what subroutine does it :D

"15 Elul 5776" into "ט''ו אלאל תשע''ו"

Avenues to investigate, maybe :D

http://grep.cpan.me/?q=Elul+ ... DateTime::Calendar::Hebrew ... Locale::Hebrew::Calendar

Maybe DateTime::Format::Strptime can be involved in a hebrew locale is supported somehow ...