Here is a horrible solution but might start you in the right direction.
You need to know the ASCII values of the ones you can't convert wit uc.
Hope there’s not very many.
my %vowels = (
132 => 142, # dec value for ascii a' / A'
138 => 144, # dec value for ascii e' / E'
141 => 73, # dec value for ascii i' / I
149 => 153, # dec value for ascii o' / O'
129 => 154, # dec value for ascii u' / U'
);
foreach ( sort keys %vowels ) {
printf "%c %c\n",$_,$vowels{$_};
}