Also, the word you were thinking of is "interpolate", not "concatenate". :)

Aye. Even though interpolation is implemented using concatenation, "strings are concatenated" while "variables are interpolated into strings".

>perl -MO=Concise -e "$a = qq{$b$c}";
8  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
7     <2> sassign vKS/2 ->8
-        <1> ex-stringify sK/1 ->6
-           <0> ex-pushmark s ->3
5           <2> concat[t4] sK/2 ->6     <----
-              <1> ex-rv2sv sK/1 ->4
3                 <#> gvsv[*b] s ->4
-              <1> ex-rv2sv sK/1 ->5
4                 <#> gvsv[*c] s ->5
-        <1> ex-rv2sv sKRM*/1 ->7
6           <#> gvsv[*a] s ->7
-e syntax OK
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