$ perl -MO=Concise,-exec -E'my $foo = "weird123"; say $foo . do { $foo =~ s/123//; $foo };'
...
6  <;> nextstate(main 49 -e:1) v:%,{,469764096
7  <0> pushmark s
8  <0> padsv[$foo:47,49] s
9  <0> enter s
a  <;> nextstate(main 48 -e:1) v:%,{,469764096
b  <0> padsv[$foo:47,49] sRM
c  <$> const[PV ""] s
d  </> subst(/"123"/) vKS
e  <;> nextstate(main 48 -e:1) v:%,{,469764096
f  <0> padsv[$foo:47,49] s
g  <@> leave sKP
h  <2> concat[t2] sK/2
i  <@> say vK
...