my %input = (
    "NaMe" => "Fred",
    "iD" => "123",
    "PET" => "Cat",
    "spoon" => "garbage",
);
my %caseCorrection =
(
    "name" => "Name",
    "id" => "ID",
    "pet" => "pet",
);
my %output;
%output = map {
        $caseCorrection{lc $_} => $input{$_}
    } grep {
        exists $caseCorrection{lc $_}
    } keys %input;

my $getString = join ";", map {
        "$_=$output{$_}"
    } keys %output;