That code comes from Re^9: bit by overhead and is identified as being slower than this:

my %cache2;
sub to_cache2 {
    my( $ticker, $data ) = @_;

    $cache2{$ticker} = [ map pack("A10FFFFL", @$_), @$data ];
}

sub from_cache2 {
    my $ticker = shift;
    return [ map unpack("A10FFFFL", $_), @{ $cache2{$ticker} } ];
}
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which you should use instead.

The suggestions I was referring to are:

Do you use all 251 sets of 6 values every time you retrieve the data from the cache?

The gist of where I'm going with this, is that if you don't use them all each time, you might be better to use a two level cache so that you unpack less data each time.

Or, if you do use all the value for each ticker each time, then could you not cache the results of whatever you do with them, rather than the raw data itself?