It doesn't say that function name will be case sensitive in VFP outside of DECLARE w/o AS clause and it is not case sensitive.

>From VFP 6.0 help:
>
>"FunctionName
>
>Specifies the name of the shared library function to register in Visual FoxPro. Function names passed in this parameter are case-sensitive."
>
>"AS AliasName
>
>Specifies an alias name for a shared library function name that has the same name as a Visual FoxPro function or is not a legal Visual FoxPro name. AliasName should not be a Visual FoxPro reserved word or the name of a shared library function already registered with Visual FoxPro.
>
>If you assign alias to the function, use the alias when calling the shared library function. AliasName is not case-sensitive."
>
>>

declare Sleep in win32api as Sleep

>makes it case insensitive
>>
>>The function name is case insensitive in VFP outside DECLARE statement.

declare Sleep in win32api integer