OK supposing you have at most 4 words in a group (otherwise expand $max_del)

use strict;
use warnings;
use Data::Dump qw/pp dd/;
use feature 'say';

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


# prepare sub-slices
my @slices;

my $max_del = 3;

for my $del ( 0 .. $max_del ) {
    for my $i (0 .. $del) {
        for my $l ( $i .. $del) {
            push @{ $slices[$del] }, [$i .. $l]
              unless $i==0 and $l == $del; # exclude identity
        }
    }
}

sub partitions {
    my $group =shift;
    my @words = split / /,$group;
    return map { join " ", @words[@$_] } @{$slices[$#words]}
}

delete @hash{ partitions($_) } for keys %hash ;

say "Result: ", pp \%hash;

say "# --- tests";

say '@slices = ', pp \@slices;

say "partitions('automation technology process limit') = " ,
  pp partitions('automation technology process limit');

[download]

Result: {
  "automation technology process" => 3,
  "mass creation" => 2,
  "rendition" => 3,
  "saturation" => 3,
}
# --- tests
@slices = [
  [],
  [[0], [1]],
  [[0], [0, 1], [1], [1, 2], [2]],
  [[0], [0, 1], [0, 1, 2], [1], [1, 2], [1, 2, 3], [2], [2, 3], [3]],
]
partitions('automation technology process limit') = (
  "automation",
  "automation technology",
  "automation technology process",
  "technology",
  "technology process",
  "technology process limit",
  "process",
  "process limit",
  "limit",
)

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

In reply to Re^2: retain longest multi words units from hash by LanX
in thread retain longest multi words units from hash by Anonymous Monk

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