my %hash;
my $current_token = '';
$re_types = qr/(HEADER|TITLE|COMPND)/;

while (<DATA>) {
    my ($token, $value ) = $_ =~ m/^$re_types\s+(.*)/;
  next unless $token;
    if ( $token eq $current_token ) {
        ${$hash{$token}}[-1] .= ' ' . $value;
    } 
    else {
        $current_token = $token;
        push @{$hash{$token}}, $value;        
    }
}

use Data::Dumper;
print Dumper \%hash;

__DATA__
blah