perl -we "package API{$|++;$'__=__PACKAGE__;$\"=','}print/J$__/?exit:q +q($_\r)for glob qq{{@{[A..P,I]}}}x4"

Note: Win32 double quotes!

Thanks Tux, thanks Eily


PS changed the title from empty API package -- oneliner to the current

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.