The ornamental design for a perch, as shown and described.
FIG. 1 is a perspective view of a perch;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view, wherein a right side view is a mirror image of the left side view thereof;
FIG. 5 is a top view of thereof; and,
FIG. 6 is a bottom view of thereof.
The shading on the larger, upper portion of the front, rear, left and right sides of the vertical stand on FIGS. 1, 2, 3 and 4 and the bottom of the larger, upper portion of the vertical stand on FIG. 6 represents a textured surface.