Design of an AST node.

$node = { 
    type => 'Node type',
    children => [
        subnode1,
        subnode2,
        ... # other nodes
    ],
    # optional debug information
    debug => {
        file => 'filename', # if the same as the parent can be omitted
        line => 123
    }
    ... # other optional information depending on the node type 
}