Peroxy acids of sulphur are:
H2S2O8
H2SO5
For the acid to be a 'peroxy' acid, it should have a 'peroxy' linkage - much like the −O−O− bond:
Both the above are peroxy acids.
H2S2O3 is thiosulphuric acid; it is similar to sulphuric acid but one with an S−S double bond.