use strict; use warnings;
use DB_File;
use Fcntl;
use File::Temp qw(:POSIX);
use Data::Dumper;
$Data::Dumper::Indent = 1;

my $filename = tmpnam(); # temporary file
my %h;                   # tied DB_File hash

tie %h, "DB_File", $filename, O_RDWR|O_CREAT, 0666, $DB_BTREE
    or die "Cannot open $filename: $!\n";

%h = (
    'rendition' => '3',
    'automation' => '2',
    'saturation' => '3',
    'mass creation' => 2,
    'automation technology' => 2,
    'automation technology process' => 3,
);

my $prev;

for (keys %h) {
    delete $h{$prev} if $prev && /^$prev/;
    $prev = $_;
}

print Dumper(\%h);

# cleanup
untie %h;
unlink $filename;
__END__
$VAR1 = {
  'automation technology process' => '3',
  'mass creation' => '2',
  'rendition' => '3',
  'saturation' => '3'
};