8. Apparatus for string matching, comprising: an interface, which is arranged to accept an input regular expression comprising one or more nested references to respective referenced regular expressions; a regular expression processor, which is arranged to replace the nested references in the input regular expression with the respective referenced regular expressions, so as to provide a modified regular expression that does not contain a reference to another regular expression; and a parsing processor, which is arranged to match the modified regular expression to a target string.
8. Apparatus for string matching, comprising: an interface, which is arranged to accept an input regular expression comprising one or more nested references to respective referenced regular expressions; a regular expression processor, which is arranged to replace the nested references in the input regular expression with the respective referenced regular expressions, so as to provide a modified regular expression that does not contain a reference to another regular expression; and a parsing processor, which is arranged to match the modified regular expression to a target string. 9. The apparatus according to claim 8 , wherein the regular expression processor is arranged to represent the input regular expression using a character string, in which each of the nested references is represented by a pointer comprising at least one dedicated pointer character followed by a reference name.