use strict; use warnings;
use Data::Dump;

my %h = (
    'rendition' => '3',
    'automation' => '2',
    'saturation' => '3',
    'mass creation' => 2,
    'technology' => 5, 
    'process' => 6, 
    'creation' => 7,
    'saturation process' => 9,
    'automation technology' => 2,
    'automation technology process' => 3,
);  
dd 'before', \%h;

for (keys %h) {
    if (/\s/) {
        my @l = split ' ';
        for my $k (map {my $i=$_;map{join" ",@l[$i..$_]}$i..$#l}0..$#l) {
            delete $h{$k} unless $k eq $_;
        }   
    }   
}   
dd 'after', \%h;
__END__
(
  "before",
  {
    "automation"                    => 2,
    "automation technology"         => 2,
    "automation technology process" => 3,
    "creation"                      => 7,
    "mass creation"                 => 2,
    "process"                       => 6,
    "rendition"                     => 3,
    "saturation"                    => 3,
    "saturation process"            => 9,
    "technology"                    => 5,
    "technology process"            => 5,
  },
)
(
  "after",
  {
    "automation technology process" => 3,
    "mass creation" => 2,
    "rendition" => 3,
    "saturation process" => 9,
  },
)

##</code><code>##

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'
};