Slash's Wife Gunning For Half ... We DON'T Have a Prenup

Slash's rock and roll fortune could soon be sliced in half ... TMZ has learned he didn't have a prenup and his wife is gunning for half.

Sources close to Perla Ferrar tell us she's already hired a lawyer to figure out exactly how much money Slash has earned since their 2001 marriage. The lawyer and at least one pencil pusher are assessing real property, album sales and other assets.

Perla never knew specifics ... but she believes he's made 10s of millions of dollars since they married, and she's entitled to 50%.

She can't touch the G-N-R loot pre-marriage -- which is enormous -- but her claim is anything but chump change.

Slash has released 5 albums since they wed, including one with his band Velvet Revolver that went double platinum.

As we previously reported ... Slash filed for divorce last week, but that doesn't mean the fat lady has sung. He did the same thing in 2010 and withdrew his petition 2 months later.

We're told this time around Perla believes Slash has moved on -- he's already dating someone and has destroyed any chance of a reconciliation.