Ahem, this isn't going to win style points (I think), but here goes:
#! /usr/bin/perl -l

my %T = map {$_->[0] => $_} map {[split /,\s*/]} <DATA>;

sub xz4 { ["$_[0]<-$_[2]", "$_[3].$_[1]"] }
sub xln {
  my @r = @{@T{@_} // return (@_, '')};
  @{ $r[3] //= xz4 @r[0,2], xln($r[1]) };
}
print grep {s/\./= /} join " ", xln($_) for keys %T;

__DATA__
M10,    Q,    P,
M143,    M10,    P,
M406,    M143,    PL,
M407,    M143,    PL,
M420,    M143,    E,
M421,    M143,    E,

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In reply to Re: constructing a tree from csv file by oiskuu
in thread constructing a tree from csv file by zing

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