Thank you for this approach! This is about 10x faster than the next best approach that was suggested here that I tried implementing (which was this code from an AnonymousMonk): 

my %seen;
$seen{$_}++ for @observed;
@permCounts = map { $seen{$_} || 0 } @perms;

[download]

This is good enough to get me going, but I will follow the other advice that was offered and learn about fleximal, PDL::Sparse, and hash-fu. I am very grateful for the generous advice from all of you!

best,

jim

ps -- Slight tweak: abc=(0,1,2), and then 0+(1*26^1)+(2*26^2), etc. (i.e., a=0, z=25, and when string position > 0 you multiply the index of the character in that position by 26 raised to the power of the position).

In reply to Re^2: counting instances of one array in another array by jsmagnuson
in thread counting instances of one array in another array by jsmagnuson

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