Re^2: strange usage of s///

Perl v5.18.1 handles them as one would expect:

perl -MO=Deparse -e '$_="abcdef"; s/@{[s".."."gr]}\K$"//; print'
$_ = 'abcdef';
s[@{[s/.././gr];}\K$"][];
print $_;
-e syntax OK
[download]

perl -MO=Deparse -e '$_="abcdef"; s/@{[s".."."gr]}\K //; print'
$_ = 'abcdef';
s[@{[s/.././gr];}\K ][];
print $_;
-e syntax OK
[download]

PS: With Perl v5.14.2 I get the same result as you.

(Testing environment was 64bit Linux in both cases.)

So yeah, strange indeed...