A further important point is that a character class defined inside square brackets only matches one single character in the text, so [250-370] matches either a '2', or a '5', or '0','1','2','3' (0-3), or a '7', or a '0'. To match more than one character you use a quantifier, of which + (one or more), * (zero or more), and {4} (exactly 4) are examples.