Find columns referenced by virtual column expression
User_tab_cols shows that there is a dependancy when virtual_column contains 'YES', which answers your need to determine if there is any dependency at all.

In order to determine what the actual virtual column consists of, one still needs to parse data_default.

SELECT column_name
  ,      virtual_column
  ,      segment_column_id
  ,      internal_column_id
  FROM   user_tab_cols
  WHERE  table_name = 'T'
  ORDER  BY column_id;