% perl-v5.32.1 -e 'use warnings; \
  BEGIN { printf "%vx\n", ${^WARNING_BITS} }'
55.55.55.55.55.55.55.55.55.55.55.55.55.55.55.55.55.55.55
% perl-v5.32.1 -e 'use warnings; no warnings "recursion"; \
  BEGIN { printf "%vx\n", ${^WARNING_BITS} }'
55.55.55.55.45.55.55.55.55.55.55.55.55.55.55.55.55.55.55
% # from which I derive:
% perl-v5.32.1 -e 'use warnings; BEGIN {
  printf "recursion warnings are %senabled\n",
    (0x10 & ord substr ${^WARNING_BITS}, 4, 1) ? "" : "not "
}'
recursion warnings are enabled
%