I tried almost the same thing with the same result:

my %cache3;
sub to_cache3 {
    my( $ticker, $data ) = @_;

    $cache3{$ticker} = pack "(A10FFFFL)*", map @$_, @$data;
}

sub from_cache3 {
    my $ticker = shift;
    return [ 
        map[ 
            unpack("A10FFFFL", $_) 
        ], unpack '(A[A10FFFFL])*', $cache3{$ticker} 
    ];
}

C:\test>880868-2
       Rate mod2 orig mod1
mod2 18.9/s   --  -3% -76%
orig 19.4/s   3%   -- -75%
mod1 78.5/s 316% 304%   --
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