Looks like 5.10 according to perl5100delta: 

    Relative backreferences
        A new syntax "\g{N}" or "\gN" where "N" is a decimal integer a
+llows
        a safer form of back-reference notation as well as allowing re
+lative
        backreferences. This should make it easier to generate and emb
+ed
        patterns that contain backreferences. See "Capture buffers" in
        perlre. (Yves Orton)

[download]

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re^3: Refer by relative way to regex group (eg. the last one) by Fletch
in thread Refer by relative way to regex group (eg. the last one) by Anonymous Monk

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