And, if there's nothing in the string to interpolate, perl changes the double quotes to single quotes:

zippy:~/scripts$ deparse -e '$h{q[one]} = 1; $h{qq[two]} = 2; $x = q[t
+hr]; $h{qq[${x}ee]} = 3;'
$h{'one'} = 1;
$h{'two'} = 2;
$x = 'thr';
$h{"${x}ee"} = 3;
-e syntax OK
[download]