$self is a scalar variable, so it's not a hash, it's a reference to a hash. You need to dereference it to get the hash:

print map { "Key: $_ has Value:$self->{$_}\n" } keys %$self;
#                                   ~~               ~
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Or, use Data::Dumper:

use Data::Dumper;
...
print Dumper($self);
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