This might not be exactly what you want but it was fun anyways :)

Done without looking at hints or other code.

Runs in xterm on ArchLinux, don't know about other systems...

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11150326
use warnings;
use List::Util qw( uniq );
use Term::ReadKey;

# dummy items to play with
my @animals = (qw( cow camel dog cat  ));
my @foods   = (qw( fish pasture meat  ));
my @places  = (qw( wood sea    desert ));

# commands
my $commands = {
    select => {
        completion_list => \@animals,
        commands => {
                        give => { completion_list => \@foods, },
                        take_to => { completion_list => \@places, },
        },
    },
    kill  => { completion_list => \@animals, }
};

my $completed = autocomplete( $commands, 'test autocomplete> ' );
print $completed ? "\nThe user entered: $completed\n" : "\nEscape\n";
exit;

######################################################################

sub autocomplete
  {
  my ($commands, $prompt) = @_;
  my $lines = join "\n", lines($commands), '';
  $prompt //= '> ';
  my $input = '';
  my $clearline = "\e[G\e[K";
  my $skip;
  $| = 1;
  ReadMode 'raw';
  eval
    {
    while()
      {
      $skip or print $clearline, $prompt, $input;
      $skip = 0;
      my $char = ReadKey;
      $char =~ tr/\e\cc// and $input = '', last;
      $char =~ tr/\n\r// and $lines =~ /^$input$/m ? last : next;
      $char eq "\b" and chop($input), next;
      if( $char eq "\t" )
        {
        my ($new, $letters) = extend($input, $lines);
        if( not defined $new )
          {
          # shorten to longest legal string
          $input = "$input\n$lines" =~ /^(.*).*\n(?:.*\n)*\1/ ? $1 : '
+';
          next;
          }
        $input = $new;
        my $info = (extend($input, $lines))[1] || '***Complete!';
        my $len = 2 + length $info;
        print $clearline, $prompt, $input, "  \e[92m$info\e[m\e[${len}
+D";
        $skip = 1;
        next;
        }
      $input .= $char;
      }
    };
  ReadMode 'restore';
  print "\n";
  return $input;
  }

sub extend
  {
  my ($in, $lines) = @_;
  my $match = join '', $lines =~ /^\Q$in\E.*\n/gm;
  my $extend = $match =~ /^(.*).*\n(?:\1.*\n)*\z/? $1 : undef;
  my $letters = join ' ', sort + uniq $lines =~ /^\Q$in\E(\S+)/gm;
  return $extend, $letters;
  }

sub lines
  {
  my $cmd = shift or return '';
  map s/ +$//r, map { my $key = $_; # fun triple map nesting
    map { my $prev = $_;
      map "$key $_ $prev", @{ $cmd->{$key}{completion_list} };
      } lines( $cmd->{$key}{commands} )
    } keys %$cmd;
  }
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