Minor change:

#! perl -sw
use 5.010;

$data = do { local $/ = undef; <DATA> };

my $x = [map \$_,
        scalar($data =~ s/(\w+)/$1/g),
        scalar($data =~ s/\n/\n/g),
];

say "@$x";

my $y = [map \$_,
        scalar($data =~ s/\n/\n/g),
        scalar($data =~ s/(\w+)/$1/g),
];

say "@$y";

__DATA__
Line1 Word Something
Line2 Other Word
[download]

SCALAR(0x2392c4) SCALAR(0x239224)
SCALAR(0x239314) SCALAR(0x239314)
[download]

The Ys use the same variable for the return value, but not the Xs.

I don't actually know *why* the two calls return the same variable.

Interestingly, the problem goes away if the captures are removed.

Update: There has been a change in the relevant code since 5.10.0, but it appears to be an optimisation and not a fix.

5.10.0:
PUSHs(sv_2mortal(newSViv((I32)iters)));

maint-5.10 as it stands right now:
mPUSHi((I32)iters);

Patch

In both case, it looks like the operator always returns a new SV, so maybe there's some stack corruption??