$ perl -Mdiagnostics -e "s//1/g for 1"
Modification of a read-only value attempted at -e line 1 (#1)
    (F) You tried, directly or indirectly, to change the value of a
    constant.  You didn't, of course, try "2 = 1", because the compile
+r
    catches that.  But an easy way to do the same thing is:

        sub mod { $_[0] = 1 }
        mod(2);

    Another way is to assign to a substr() that's off the end of the s
+tring.

    Yet another way is to assign to a foreach loop VAR when VAR
    is aliased to a constant in the look LIST:

            $x = 1;
            foreach my $n ($x, 2) {
                $n *= 2; # modifies the $x, but fails on attempt to mo
+dify the 2
            }

Uncaught exception from user code:
        Modification of a read-only value attempted at -e line 1.
 at -e line 1
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