If you're separating your data by --, you don't even need the size information.

use Data::Dumper;

use strict;

my @array;
my $i = 0;

while (<DATA>) {
    chomp;
    
    # Skip header row
    if (!$i++) {
        next;
    
    # End of Data Structure.
    } elsif (/^-*$/) {
        print Dumper(\@array);
        @array = ();
        $i = 0;
        
    # Add to data
    } else {
        push @array, [split / /];
    }
}

print Dumper(\@array);

__DATA__
3 3
3 6 5
2 4 5
1 5 7
--
2 4
1 4 5 9
3 8 6 8
--
5 3
1 5 3
7 3 6
4 7 9
1 2 3
5 7 1
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