For those working on their golf (or who just like some of the fun things that Perl can do), here's your exact code in 3 (Perl) lines.

my (@only_in_foo, @kv_different, @kv_equal);
push( @{
    exists $bar{$_} 
    ? $bar{$_} eq $foo{$_} 
        ? \@kv_equal 
        : \@kv_different 
    : \@only_in_foo}, $_) for keys %foo;
my @only_in_bar = grep { ! exists $foo{$_} } keys %bar;
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