You may find the following code helpful:

use strict;
use warnings;

my @list = qw(20 60 65 50 55 70 10 30 40 90 51 52);
my @runs;

for my $item (@list) {
    my @newRuns = [$item];
    
    for my $run (@runs) {
        next if $item <= $run->[-1];
        
        push @newRuns, [@$run];
        push @$run, $item;
    }
    
    push @runs, @newRuns;
}

@runs = sort {@$a <=> @$b} @runs;
@runs = grep {@{$runs[-1]} == @$_} @runs;

print "@$_\n" for @runs;
[download]

Prints:

20 60 65 70 90
20 50 55 70 90
20 30 40 51 52
10 30 40 51 52
[download]