> There's something about going from the first completed permutation, resulting in $perm = abcd, to the next line of output, where the $perm is now abd, missing the c.

In short: Level4 calls Level5 only one time, always! This means 4 returns to Level3 immediately after 5 returns.

And Level3 calls Level4 for the second time, but now with $perm="ab"."d" .

I hope it's clearer now, have a look at the extensive explanations in my other replies, especially the nested loop analogy.

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

In reply to Re^3: Please help me understand this permutation sub? by LanX
in thread Please help me understand this permutation sub? by mdunnbass

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