Because letters and digits have a logical order, you can abbreviate those by specifying ranges of them: [a-c] is equal to [abc] and [0-9] is equal to [0123456789]. Combining these constructs, for example [a-fynot1-38] is completely legal (the last one would match, of course, either of a, b, c, d, e, f, y, n, o, t, 1, 2, 3 or 8).
Com les lletres i els números tenen un ordre lògic, ho podeu abreujar usant intervals: [a- c] és igual a [abc] i [0- 9] és igual a [0123456789]. Combinant aquestes construccions, per exemple [a- fynot1- 38] resulta completament vàlid (aquesta última hauria de coincidir amb qualsevol dels caràcters o dígits a, b, c, d, e, f, y, n, o, t, 1, 2, 3 o 8).