for my $hashref (@$sur) {
  if (exists $hash1{$hashref->{three}}) {
    $hash1{$hashref->{three}} .= "####$hashref->{four}";
  }
  else {
    $hash1{$hashref->{three}} = join '<-->', map $hashref->{$_}, (qw(one two four));
  }
}