>perl -wMstrict -le
"for (@ARGV) {
   s{ (?<= [[:upper:]]) ([[:upper:]]+) }{\L$1}xmsg;
   print;
   }
"
"XYZZY"  "RUN4LIFE"  "RUN42LIFE CO"
"GENERAL WIDGET CO., INTL"  "MI-GO BRAIN CYLINDERS, IPTY."
Xyzzy
Run4Life
Run42Life Co
General Widget Co., Intl
Mi-Go Brain Cylinders, Ipty.