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rpartition 

        # String.rpartition

(from ruby core)
---
    str.rpartition(sep)             -> [head, sep, tail]
    str.rpartition(regexp)          -> [head, match, tail]

---

Searches *sep* or pattern (*regexp*) in the string from the end of the
string, and returns the part before it, the match, and the part after
it. If it is not found, returns two empty strings and *str*.

    "hello".rpartition("l")         #=> ["hel", "l", "o"]
    "hello".rpartition("x")         #=> ["", "", "hello"]
    "hello".rpartition(/.l/)        #=> ["he", "ll", "o"]

The match from the end means starting at the possible last position, not
the last of longest matches.

    "hello".rpartition(/l+/)        #=> ["hel", "l", "o"]

To partition at the last longest match, needs to combine with negative
lookbehind.

    "hello".rpartition(/(?<!l)l+/)  #=> ["he", "ll", "o"]

Or String#partition with negative lookforward.

    "hello".partition(/l+(?!.*l)/)  #=> ["he", "ll", "o"]

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