>>400 Perl5

use feature say;
for (<DATA>) {
 say map{ucfirst lc} /((?:\d_\d|[^_\s])+)/g;
}
__DATA__
snake_case
ODAI00_99_TEST
x_0_x
UpperCamelCase


実行結果
~ $ perl 15_400.pl
SnakeCase
Odai00_99Test
X0X
Uppercamelcase