Thanks for the responses

I was also trying to use the recursive functions to read and print from the data file.

The code doesn't have the logic to build the tree but I was trying to get the sequence correctly.

Looking at your scripts, I think I should scrap this and look to build on what you provided.

Below is the code:-

my @arr = ( 'NA', 'EU' );
my $base = 'Countries';

process_full_list( $base, @arr );

sub process_full_list {
    
    my ($base1, @arr1 ) = @_;
   
    my $elem;  

    print "############################\n";
    print "In process full list: $base1 : @arr1\n";
    print "############################\n";
     
    foreach $elem ( @arr1 ) {
       process_next( $base1, $elem);
     }
}

sub process_next {
  
   my ( $r_base, $r_elem ) = @_;
   my ( $new_base, $new_elem, @new_arr);

   print "\tIn process next: $r_base : $r_elem\n";
    
    # The if loop is temporary. It will be replaced by a 
    # sub that will fetch the next array to process by 
    # reading from the file based on the search string.
   if ( $r_elem eq 'NA' ) {
       @new_arr = ( 'US', 'CA' );
   }
   elsif ( $r_elem eq 'EU') {
       @new_arr = ( 'FR', 'IT' );
   }
   elsif ( $r_elem eq 'US') {
       @new_arr = ( 'NY', 'LA' );
   }
   elsif ( $r_elem eq 'CA') {
       @new_arr = ( 'TO', 'VC' );
   }
  
    if( defined ( $r_elem ) && (@new_arr) ) {
      print "\tnew_base = $r_elem: new_arr=@new_arr\n";
      process_full_list( $r_elem, @new_arr );
   }
      
}
[download]

The output for the above is

###########################################
In process full list: Countries : NA EU
###########################################
        In process next: Countries : NA
        new_base = NA: new_arr=US CA
###########################################
In process full list: NA : US CA
###########################################
        In process next: NA : US
        new_base = US: new_arr=NY LA
###########################################
In process full list: US : NY LA
###########################################
        In process next: US : NY
        In process next: US : LA
        In process next: NA : CA
        new_base = CA: new_arr=TO VC
###########################################
In process full list: CA : TO VC
###########################################
        In process next: CA : TO
        In process next: CA : VC
        In process next: Countries : EU
        new_base = EU: new_arr=FR IT
###########################################
In process full list: EU : FR IT
###########################################
        In process next: EU : FR
        In process next: EU : IT
[download]