StringInsert

WMA link


StringInsert["string“, ”snew", n]

yields a string with snew inserted starting at position n in string.

StringInsert["string“, ”snew", -n]

inserts a at position n from the end of "string".

StringInsert["string“, ”snew", {$n_1$, $n_2$, ...}]

inserts a copy of snew at each position $n_i$ in string;
the $n_i$ are taken before any insertion is done.

StringInsert[{$s_1$, $s_2$, ...}, "snew", n]

gives the list of results for each of the $s_i$.

Insert dot as millar separators

StringDrop
StringJoin