readonly: no
Modification of a read-only value attempted at - line 9.
# Successfully installed JSON-4.02 (upgraded from 2.97001)
readonly: no
Modification of a read-only value attempted at - line 8.
# Scalar::Util is up to date. (1.50)
perl -MScalar::Util=readonly -MJSON -E 'say readonly(JSON::false) ? "readonly" : "ReAdOnLY"'
ReAdOnLY
# This is perl 5, version 18, subversion 4 (v5.18.4)