Perth scored twice in the first 16 minutes and dealt competently with Victory's attacks to take away a precious win from Simonds Park in Geelong.
After this defeat Victory is still in second place but its title credentials suffered a blow as Glory gave a clear demonstration of its overall strength.
Both teams settled quickly into an effective passing game with Victory as expected forcing the pace.
Perth however took a shock lead after seven minutes when striker Andy Keogh held off a challenge from Adrian Leijer and when it looked like he had taken too much time to pull the trigger he found enough space to place the ball in the far corner despite Nathan Coe's attempt to save.
Chris Harold then ran well into space to pick up a gem of a pass from Nebojsa Marinkovic, round Coe and slot the ball home with composure to put Glory two up after 16 minutes.
Victory was shocked by this turn of events and Gui Finkler had an opportunity to reduce the margin with a free kick from his favourite position but his dipping shot went wide.
Besart Berisha then put Archie Thompson through down the middle but the striker's shot was parried by well positioned Danny Vukovic.
Victory was enjoying a good period and after 32 minutes a magnificent team move involving Finkler and Berisha ended with Kosta Barbarouses crossing poorly to spoil a highly promising attack.
Six minutes from halftime Berisha beat two defenders with deft footwork and put Thompson through again but the former Socceroos striker, who was deputising for suspended Fahid Ben Khalfallah, shot hopelessly wide from an excellent position before the linesman saved his blushes by raising the offside flag.
Victory finished an entertaining half on top of its rival but Glory's defence was holding up very well.
The home team got the breakthrough it needed after 56 minutes when Finkler was upended in the penalty area by Scott Jamieson and Berisha converted the subsequent spotkick with ease, sending Vukovic the wrong way.
Victory was right back in the game and Finkler played a defence-splitting pass to Barbarouses but the winger wasted an opportunity by taking the wrong option before Harold had a chance to restore Perth's two-goal lead ... his firm drive was well saved by Coe.
Thompson was unlucky with a difficult header that skimmed the top part of the bar as Victory pushed forward for an equaliser with the support of a 21,289 crowd.
The league leader however was not prepared to urrnder the initiative and redoubed its efforts in midfield, Ruben Zadkovich testing Coe with a crisp shot from outside the penalty area.
Berisha, who was Victory's best player by a mile, created a chance for himself four minutes from time but after forcing his way into Glory's penalty area he shot at the side netting.
