# more or less untested
my $hash = {};
pushref($hash, qw(one two three));
sub pushref {
  my ($hash,@array) = @_;
  my $ref = \$hash;
  for (@array) {
    $ref = \$$ref->{$_};
  }
  $$ref = 1;
  $_[0] = $hash;
}

# UPDATE: simplified and tested
my $hash = {};
my $ref = \$hash;
for (qw(one two three)) {
  $ref = \$$ref->{$_};
}
$$ref = 1;
print Dumper $hash;
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