This returns all maximal ordered subsets: 

sub MaxOrderedSubList {
    my @order= @{ shift @_ };
    my %order;
    @order{@order}= 0..$#order;
    my @list= @{ shift @_ };
    my @wins= ( [] );
    my @idx= ( -1 );
    my $i= 0;
    while(  1  ) {
        do {
            ++$idx[$i];
            if(  $#list < $idx[$i]  ) {
                if(  --$i < 0  ) {
                    return @wins;
                }
                redo;
            }
        } while(  0 < $i
            &&  $order{$list[$idx[$i]]}
                    <= $order{$list[$idx[$i-1]]}  );
        if(  $#{$wins[0]} <= $i  ) {
            @wins= ()   if  $#{$wins[0]} < $i;
            push @wins, [ @list[@idx[0..$i]] ];
        }
        $idx[$i+1]= $idx[$i];
        ++$i;
    }
}

for my $win (  MaxOrderedSubList(
    [1,2,3,8,4,5,6], [2,1,3,5,4] )
) {
    print "@$win\n";
}

for my $win (  MaxOrderedSubList(
    [qw( t h i s w o r k a )], [qw( w h a t i s o k )] )
) {
    print "@$win\n";
}

[download]
Output: 
2 3 5
2 3 4
1 3 5
1 3 4
h i s o k
t i s o k

[download]
The maximum size for ordered subsets would be 0 + @{( MaxOrderedSubList( [...], [...] ) )[0]} (updated)

        - tye

In reply to (tye)Re2: Items in Order by tye
in thread Items in Order by artist

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