You could split on anything that wasn't an uppercase letter ([^A-Z]), capturing what you split on, do your ucfirst lc in a map then concatenate the results with join.

$ cat companies
WOOLWORTHS
CAP GEMINI
AVIVA
AMERADA HESS
RUN4LIFE
$ perl -pi.bak -e '$_ = join q{}, map { ucfirst lc } split m{([^A-Z]+)
+};' companies 
$ cat companies
Woolworths
Cap Gemini
Aviva
Amerada Hess
Run4Life
$
[download]

I hope this is useful.