[suzeeq]

When you slip purlwise (or knitwise) that only refers to how the needle is inserted into the stitch, has nothing to do with where the yarn is. So leave the yarn in back and you're ready for the knits after it. Putting the yarn in front leaves the strand in front of the stitch - sometimes this is done as part of a design, but probably not for socks.

eta - leave the yarn in back on the knit row, it can be left in the front on the purl row.