Perl does parse the string, in the case of double quotes. (Actually, it has to parse every constant string in the program to find the closing quote, but that's not precisely what you meant):

$ perl -MO=Concise
my $foo = 'bar';
my $baz = "foo${foo}bar\n";

e  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -:1) v ->3
5     <2> sassign vKS/2 ->6
3        <$> const[PV "bar"] s ->4
4        <0> padsv[$foo:1,3] sRM*/LVINTRO ->5
6     <;> nextstate(main 2 -:2) v ->7
d     <2> sassign vKS/2 ->e
-        <1> ex-stringify sK/1 ->c
-           <0> ex-pushmark s ->7
b           <2> concat[t4] sKS/2 ->c
9              <2> concat[t3] sK/2 ->a
7                 <$> const[PV "foo"] s ->8
8                 <0> padsv[$foo:1,3] s ->9
a              <$> const[PV "bar\n"] s ->b
c        <0> padsv[$baz:2,3] sRM*/LVINTRO ->d
- syntax OK
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I guess you didn't look at the rest of this thread. Of course Perl would parse it in the case of double quotes, and that would prevent the problem in the first place.

The double quotes in the root node were (necessarily) a mis-copy.

- tye