use Text::CSV_XS;
use IO::File;

my $csv = new Text::CSV_XS({sep_char=>"\x1E", escape_char=>"\x10"});

my $io  = new IO::File('< flat_file.txt');

until ($io->eof) {
   my $line = $io->getline();
   $line =~ s/_UNSC/\x10/g;
   $line =~ s/(?<!\x10) _ /\x1E/g;

   my $column = $csv->parse($line);
   ## .. do something with the ArrayRef $column .. ##
}