Without it, the best way I have found to get this value is by adding it to a grid and pulling the dimension value from that column/row. For example, if your periods are in the columns and you are need the value of a substitution variable that holds the current month, add the substitution variable to the first column for the variable that holds the current month of actuals, and hide the column so the users are not confused with its purpose/location. If you make use of getCellWithMember, and don’t pass it any parameters, it will pull the top left cell in the grid, even if it is hidden. Since this is a period member, use the getPeriodName method. If it is a custom dimension, the getMemberName will provide what you need.
Here is an example. The grid’s first column is hidden, and the period is set the substitution variable that represents the last month of actuals for the year.
String sCurMonth = '"' + operation.grid.getCellWithMembers().getPeriodName() + '"' - OR - String sCurMonth = '"' + operation.grid.getCellWithMembers().getMemberName("Period") + '"'
The sCurMonth variable can be used where needed in the Groovy calculation to obtain the substitution variable value.