Yes, yes, the loop variable in for(each) aliases elements of the list.

But why is the loop variable read-only if there is only a single numeric (or string) literal in the list?

AFAICT the program works as expected in all other cases. 
perl -MDevel::Peek -le 'for my $x ([1]->[0]) {Dump $x; $x = pack "I", 
+$x; Dump $x}'         # OK
perl -MDevel::Peek -le 'my $y=1; for my $x ($y) {Dump $x; $x = pack "I
+", $x; Dump $x}'      # OK
perl -MDevel::Peek -le 'sub one(){1} for my $x (one) {Dump $x; $x = pa
+ck "I", $x; Dump $x}' # OK
perl -MDevel::Peek -le 'for my $x (0+1) {Dump $x; $x = pack "I", $x; D
+ump $x}'              # OK!!!
perl -MDevel::Peek -le 'for my $x ("1"."1") {Dump $x; $x = pack "I", $
+x; Dump $x}'          # OK

perl -MDevel::Peek -le 'for my $x ("1") {Dump $x; $x = pack "I", $x; D
+ump $x}'              # Error, read-only
perl -MDevel::Peek -le 'for my $x (1) {Dump $x; $x = pack "I", $x; Dum
+p $x}'                # Error, read-only

[download]

Experimenting on perlbanjo.com, it seems that this behavior goes back to at least Perl 5.8.

In reply to Re^2: Modification of a read-only value attempted?!? by kikuchiyo
in thread Modification of a read-only value attempted?!? by kikuchiyo

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