One alternative in the Wolfram Language is called StringExpresions. For instance, something like StringReplace["Mad Hatter", "M"|"H"~~a_~~b_..:>"B"<>a<>"g"]

One alternative in the Wolfram Language is called StringExpresions. For instance, something like StringReplace["Mad Hatter", "M"|"H"~~a_~~b_..:>"B"<>a<>"g"] returns "Bag Bager" The nice thing is that a string expression can use a RegularExpression as part of the pattern, but it's often not neccesary.