string.part_match(int, string) checks, if a string contains a substring at a certain position. No copy of any string is made in order to perform this test. This is faster than first extracting a substring of the first string and then matching it against the other. The empty string matches at all positions, even at the position after the laster character.
string.part_match(int i, char achar) is a variant that exists for polymorphic programming and handles the case, that the substring to be checked is given as single character.
"hello-world".part_match(6, "wor") == true "abcde".part_match(5, "") == true "hello.htm".part_match(6, "html") == false