Searching and replacing strings using regular expressions

My wife enjoyed the Matching strings by regular expressions recipe very much. But, she wanted more and told me that I'll get no food until I promote the recipe to be able to replace parts of the input string according to a regex match.

Ok, here it comes. Each matched sub-expression (part of the regex in parenthesis) must get a unique number starting from 1; this number would be used to create a new string.

This is how an updated program should work like:

 Available regex syntaxes:

 [0] Perl
 [1] Perl case insensitive
 [2] POSIX extended
 [3] POSIX extended case insensitive
 [4] POSIX basic
 [5] POSIX basic case insensitive

 Choose regex syntax: 0
 Input regex: (\d)(\d)
 String to match: 00
 MATCH: 0, 0,
 Replace pattern: \1#\2
 RESULT: 0#0
 String to match: 42
 MATCH: 4, 2,
 Replace pattern: ###\1-\1-\2-\1-\1###
 RESULT: ###4-4-2-4-4###

Getting ready

We'll be reusing the code from the Matching strings by regular expressions recipe. It is...