[root@host]# perl -Mre=debug -e '/12/'; Compiling REx "12" Final program: 1: EXACT <12> (3) 3: END (0) anchored "12" at 0 (checking anchored isall) minlen 2 Freeing REx: "12" [root@host]# perl -Mre=debug -e '/1+/'; Compiling REx "1+" Final program: 1: PLUS (4) 2: EXACT <1> (0) 4: END (0) anchored "1" at 0 (checking anchored) plus minlen 1 Freeing REx: "1+"