The .ST statement defines a parameter sweep, identical in function to .STEP. It is an alias supported for PSpice compatibility.
.ST [LIN] <variable> <start> <stop> <step>
.ST DEC <variable> <start> <stop> <points_per_decade>
.ST OCT <variable> <start> <stop> <points_per_octave>
.ST <variable> LIST <val1> <val2> [<val3> ...]
.ST LIN R1 100 10k 100
.ST PARAM gain LIST 1 10 100
See the .STEP documentation for full details and examples. The syntax and behavior are identical.