[perl #129208] map sometimes does and sometime does not copy vals

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I would expect these two to be equivalent:

$ ./perl -Ilib -le '$x = 4; sub {\@_; for (map {$_[0]} 1) { $_=3 } }->($x); print $x'
4
$ ./perl -Ilib -le '$x = 4; sub {\@_; for (map {shift} 1) { $_=3 } }->($x); print $x'
3

This is with v5.25.4-89-g05bda26, but the behaviour is ancient.  I get the same results with 5.8.7.

Depending on internal flags, map may or may not copy the value returned from the block.

I believe it should always copy, but I wanted to check to make sure before making the change.

-- 

Father Chrysostomos

• [perl #129208] map sometimes does and sometime does not copy vals by Father Chrysostomos
• Re: [perl #129208] map sometimes does and sometime does not copyvals by Zefram
• [perl #129208] map sometimes does and sometime does not copy vals by Father Chrysostomos via RT