my @lines;
my %seen;
while (<DATA>) {
  chomp;
  my ($onetwo,$three) = $_=~/(.*)\|(.*)/;
  if ($seen{$onetwo}) {
    $lines[$seen{$onetwo} - 1] .= ",$three";
  }
  else {
    $seen{$onetwo} = push @lines, $_;
  }
}
print "$_\n" for @lines;

__DATA__
aaa|bbb|ccc
ddd|eee|fff
ddd|eee|xxxxx
hhh|iiii|jjjjjj
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