[R] help for performing regressions based on combination of predictors

[Lily]

Dear All,

I would like to perform linear regressions based on Y
and all of the combinations of the five predictors,
i.e.,(y,x1,x2),(y,x1,x3),....,(y,x1,x2,x4,x5),....,(y,x1,x2,x3,x4,x5).

Is there any quick way to do it instead of repeat
performing regressions for 31 times? Or, is there 
any method to manipulate the dataset into the 31
combinations?

Thanks for your help!