Mythryl constants largely follow C conventions:
linux$ my
eval: printf "%c %d %d %d %f %f\n" 'a' 12 012 0x12 1.2 1.0e2;
a 12 10 18 1.200000 100.000000
eval: ^D
linux$
The Boolean constants are TRUE and FALSE:
linux$ my
eval: big = TRUE;
eval: printf "It looks %s!\n" (big ?? "BIG" :: "TINY");
It looks BIG!
eval: big = FALSE;
eval: printf "It looks %s!\n" (big ?? "BIG" :: "TINY");
It looks TINY!
eval: ^D
linux$