Function to generate a String with n times the same characters

Hello,

So far, I couldn't find such a function :

StringDup("x", 10) returns "xxxxxxxxxx"
StringDup("abc", 2) returns "abcabc"

Does it even exist ?

I have tried to build one with StringRegExpReplace, but couldn't find the correct regexp :

StringRegExpReplace($string, $string, "<insert regexp here>")

Thank you for your help !