"Universal tolower()" doesn't even make sense. What would you expect from tolower("Σ"), "σ" or "ς"? If you assume tolower(toupper(mychar)) == tolower(mychar)

"Universal tolower()" doesn't even make sense. What would you expect from tolower("Σ"), "σ" or "ς"? If you assume tolower(toupper(mychar)) == tolower(mychar) then your code is going to break.