You use integers in getangles so pack them as integers.

# my $packedRow= pack("f$width", @$avRow);
 my $packedRow= pack("i$width", @$avRow);
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You want to add each row to packedMatrix rather than overwrite it each time.

# $packedMatrix = pack("p", $packedRow);
 $packedMatrix .= pack("P", $packedRow);
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With these changes the code works on my machine.