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Postings from October 2016
On Wed, Oct 19, 2016 at 3:13 AM, Dave Mitchell <davem@iabyn.com> wrote:
>
> There's one further issue I've noticed: undef on the LHS:
>
> sub inc { $_++ for @_ }
>
> inc($a, undef ); # "Modification of a read-only value
> attempted"
> inc(($a, undef) = ($x, $y)); # increments $a and $y
>
> I think that second call to inc should pass ($a, undef) rather than
> ($a, $y) to inc, and should also die with "Modification of a read-only
> value attempted".
Undef appears to be special in that it gets replaced with an alias to the
RHS element instead of throwing a compile-time error.
$ perl -le '$x=$y=1; ($a,undef) = ($x,$y) ; print "a:$a x:$x y:$y"'
a:1 x:1 y:1
$ perl -le '$x=$y=1; ($a,2) = ($x,$y) ; print "a:$a x:$x y:$y"'
Can't modify constant item in list assignment at -e line 1, near ") ;"
Execution of -e aborted due to compilation errors.
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