diff --git a/src/main.rs b/src/main.rs
--- a/src/main.rs
+++ b/src/main.rs
@@ -31,7 +31,22 @@ fn main() {
 				}
 			};
 			println!("{}", r.eval(args[3].to_string()));
-		}
+		},
+		"compare" => {
+			let r1 = match Regexp::new(&args[2].to_string()) {
+				Ok(r) => r.determinize().reduce().normalize(),
+				Err(e) => {
+					panic!("ERROR: {e}");
+				}
+			};
+			let r2 = match Regexp::new(&args[3].to_string()) {
+				Ok(r) => r.determinize().reduce().normalize(),
+				Err(e) => {
+					panic!("ERROR: {e}");
+				}
+			};
+			println!("{}", r1.find_distinguishing_string(&r2).unwrap_or("None".to_string()));
+		},
 		s => {
 			println!("An unknown command: \"{s}\". Use \"match\" or \"test\".")
 		}