That would be surprsing, it's compiled to the same op-code.

C:\WINDOWS\System32>perl -MO=Deparse -e"$$x{key}"
$x->{'key'};
-e syntax OK

C:\WINDOWS\System32>perl -MO=Concise -e"$$x{key}"
4  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter v ->2
2     <;> nextstate(main 1 -e:1) v:{ ->3
-     <1> ex-helem vK/2 ->4
3        <+> multideref($x->{"key"}) vK ->4
-           <0> ex-gv s ->3
-e syntax OK

C:\WINDOWS\System32>perl -MO=Concise -e"$x->{key}"
4  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter v ->2
2     <;> nextstate(main 1 -e:1) v:{ ->3
-     <1> ex-helem vK/2 ->4
3        <+> multideref($x->{"key"}) vK ->4
-           <0> ex-gv s ->3
-e syntax OK

C:\WINDOWS\System32>
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