my $root = [ [ ['a','b'], [ [[['c','d'],[['e','f'],'g']],[['h',['i',['j','k']]],'l']], [['m',['n',['o','p']]],'q'] ] ], [ [ [ [[[['r',[['s','t'],'u']],'v'],['w','x']],[['y','z']]], [ ['1',[['2','3'],[['4','5'],[['6',['7',['8','9']]],['A','B']]]]], [[['C','D'],['E','F']],'G'] ] ], [ [ [['H',[['I',['J','K']],'L']],[['M','N'],'O']], ['P',[[[['Q','R'],['S','T']],'U'],['V','W']]] ], ['X','Y'] ] ],'Z' ] ] ;