AFAICT (after having played around a bit with the module), Algorithm::Knapsack only seems to compute exact solutions (i.e. where capacity is filled entirely), an approach which might not be efficiently applicable to a set of real world file sizes... Also, the computation time gets prohibitively long for file sets as shown below.

So, here's another approach using the related Algorithm::Bucketizer.  Note that this module doesn't claim to provide optimal solutions (in the sense of the knapsack problem).  But most likely good enough for most practical purposes:

#!/usr/bin/perl
use strict;
use warnings;
use Algorithm::Bucketizer;

my @filesizes = map { (stat)[7] } glob "8*.pl";
print "input (file sizes):\n@filesizes\n\n";

my $b = Algorithm::Bucketizer->new(
    bucketsize => 10_000,
    algorithm  => "retry",
);

for my $i (0..$#filesizes) {
    $b->add_item($i, $filesizes[$i]);
}

$b->optimize(
    algorithm  => "random",
    maxrounds  => 1000, 
);

print "total = file sizes...\n";
for my $bucket ($b->buckets()) {

    my $total = $bucket->level();
    print "$total = @filesizes[ $bucket->items() ]\n";
}

__END__
input (file sizes):
361 1304 1988 200 132 715 236 603 674 200 319 319 508 1027 291 154 206
+ 1781 735 2625 424 999 1152 110 43 79 421 181 1240 667 67 1085 179 13
+0 593 2240 2925 182 189 566 414 1833 898 1689 4959 87 513 111 1769 91
+0 262 2129 573 2506 363 325 4044 5298 193 298 195 132 826 229 294 198
+ 103 857 898 172 89 117 11211 693 390 663 482 1523 387 1121 188 1197 
+283 2530 459 1643 1265 636 146 8735 852 2584 372 781 1257 886 174 176
+ 637 601 466 1327 164 134 962 1340

total = file sizes...
9959 = 134 2925 513 1340 466 603 424 910 1327 229 193 43 852
9972 = 1769 319 67 1689 1121 130 110 2584 283 1304 390 206
9947 = 667 826 459 1265 674 262 372 508 1240 154 89 236 189 181 1197 7
+81 715 132
9988 = 8735 387 573 176 117
9956 = 4044 1781 174 2240 898 87 179 421 132
9953 = 1152 1257 1643 195 886 663 693 414 198 735 482 566 319 200 79 1
+11 172 188
9974 = 2129 1988 898 4959
9987 = 5298 637 1085 2530 291 146
9942 = 2625 999 1523 593 857 363 2506 182 294
6149 = 1833 164 601 962 200 325 1027 298 103 636
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