A local law change a few years ago has produced a salvo of quirky small bars that are distinctly Melbourne-ish in their hipness. They're sprouting all over the place, including in the formerly deserted-after-dark central city. Northbridge is also a happy hunting ground for more idiosyncratic drinking establishments. Many offer interesting and tasty food, too.
Northbridge is the rough-edged hub of Perth's nightlife, with pubs and clubs around William and James Sts. Recent openings have lifted the tone of the area. Most pubs have lockouts, so you'll need to be in before midnight. You may need to present photo ID.