Better yet... it appears to be entirely tied to the context of the hash-assignment operation, in a totally bizzare way:

[me@host]$ perl -e '$x = [%y = (1,2,1,2)];'
Bizarre copy of ARRAY in anonlist at -e line 1.
[me@host]$ perl -e '%y = (1,2,1,2); $x = [%y];'
[me@host]$
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