This one seems to work (it hashes a reference):

use strict;

use Tie::IxHash;
use Tie::Scalar::Timeout;

my %hash;

tie %hash, "Tie::IxHash";
tie ${$hash{TIMED}}, "Tie::Scalar::Timeout", EXPIRES => '+2s';

print "hash tie  = ", tied(%hash), "\n";
print "TIMED tie = ", tied(${$hash{TIMED}}), "\n";
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Output:

hash tie  = Tie::IxHash=ARRAY(0x80f8240)
TIMED tie = Tie::Scalar::Timeout=HASH(0x81038e4)
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