I need to split a string

Usually when a person says that, he really wants to use split. I don't see why this would be an exception...

($name, $num) = split /(?=\d+$)/, $str, 2;
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This avoids all the uproar about about non-ascii characters and meets your specification exactly in that it makes no assumptions about the string prior to the digits at the end. It uses a zero-width look-ahead assertion to split without losing characters and it uses the 3 argument version of split to limit our split to two parts (otherwise a string like "abc123" would split into 4 parts.)