... open $fh ...
$csv = Text::CSV_PP->new();           # create a new CSV parser object
$csv->sep_char('|');
# look for the header line
my $line = 0;
my $col;
while ($line < 20 && defined($col = $csv->getline($fh) )) {
  if ($csv->[0] eq '#') {
      # found it
      break;
  }
  $line++;
}
unless ($line < 20 && defined($col)) {
  die "header line not found\n";
}

# process the rest of the file
while (defined($col = $csv->getline($fh))) {
  ...
}