This is actually fairly easy to parse, although it takes a couple of steps. Either of the two will work:

1. Select a character or sequence that isn't in use anywhere in the file.
2. Replace all occurances of '_UNSC_' with that character.
3. Split the line on '_'
4. Replace any occurances of that character in any of the fields with '_'

or

1. Select a character or sequence that isn't in use anywhere in the file.
2. Replace all occurances of '_' with that sequence.
3. Replace all occurances of (sequence)UNSC(sequence) with '_'.
4. Split on (sequence)

Sometimes, your problems don't fit into a module, and you just have to roll your own:

my $character = '°';
while ( my $line = <FILE> ) {
  chomp $line;
  $line =~ s/_/$character/go;
  $line =~ s/${character}UNSC$character/go;
  my @fields = split /$character/, $line;
  # do something
}
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