#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11135697
use warnings;

my $structure = 
{
  "tool" => "A",
  "version" => "1.3",
  "dependencies" => [
    {
      "tool" => "B",
      "version" => "8.23",
      "dependencies" => []
    },
    {
      "tool" => "C",
      "version" => "2.1",
      "dependencies" => [
        {
          "tool" => "D",
          "version" => "1.1",
          "dependencies" => []
        }
      ]
    }
  ]
};

printsubstructure($structure);

sub printsubstructure
  {
  my $hashref = shift;
  printsubstructure($_) for @{ $hashref->{dependencies} };
  print "$hashref->{tool}/$hashref->{version}\n";
  }
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