my %result;
# preusume @ARGV is loaded with the changeNN files in the right order
while (<>) {
  if (/^L\|(\S+)\s+(.*)/) {
    $result{$1} = $2;
  } elsif (/^E\|(\S+)/) {
    $result{$1} = undef;
  } else {
    warn "I don't understand: $_";
  }
}
for (sort keys %result) {
  my $value = $result{$_};
  if (defined $value) { # last thing was a change:
    print "L|$_ $value\n";
  } else { # last thing was a delete:
    print "E|$_\n";
  }
}