• Regexes are their own mini-language
• Match letters, numbers, other characters
• Exclude certain characters from matches
• Character classes (in []) denote a possible set of characters to match
• Negate a character classes with a carat ([^abc])
• Provided character classes include:
• \d, \D for digits, non-digits
• \w, \W for word and non-word characters (letters, digits, underscore)
• \s, \S for white-space and non-space characters
• . for any character except newline

        my $string = "Did the fox jump over the dogs?";
        print "1: $string\n" if $string =~ m/[bdl]og/;     # bog, dog, log
        print "2: $string\n" if $string =~ m/dog[^s]/;     # no match
        print "3: $string\n" if $string =~ m/\s\w\w\wp\s/; # matches