Main
  Name = Countries
End

Sub
  Action = Find: NA
  Text = North America
End

Sub
  Action = Find: EU
  Text = Europe
End
---
Main
  Name = NA
End

Sub
  Action = Find: US
  Text = United States
End

Sub
  Action = Find: CA
  Text = Canada
End

Sub
  Action = Find: MX
  Text = Mexico
End
---
Main
  Name = US
End

Sub
  Action = 
  Text = Boston
End

Sub
  Action = 
  Text = Atlanta
End
---
Main
  Name = EU
End

Sub
  Action = 
  Text = France
End

etc...
[download]

I have to read 'Main', enter the value of 'Name' to a hash tree (like $ref_list{Countries} = undef ), continue to 'Sub' and if the value of 'Action' has 'Find:', then add the value of 'Text' to hash tree (like $ref_list{Countries}{North America} = undef ) and look for a 'Main' that has the 'Name' = 'NA' and continue building the tree... The final hash tree would look as shown below:-

%ref_list = ( 'Countries' => { 
        'North America' => {
            'United States' => {
                'Boston' => undef,
                'Atlanta' => undef
                },
            'Canada' => undef,
            'Mexico' => undef
            }
        'Europe' => {
                       'France' => undef
                       }
        },
          );
[download]