It's already been said above, but I'll restate it:

\d* means explicitly: "Match 0 or more digits"

That matches any sequence of characters that is "0 or more digits".

At the very beginning of your string (leftmost portion), a string matches that - an empty string '' right before "I fear that...".

Update: I guess samtregar beat me to it, but our message is the same :)

s**lil*;  $*=join'',sort split q**;  s;.*;grr; &&s+(.(.)).+$2$1+; $; =
qq-$_-;s,.*,ahc,;$,.=chop for split q,,,reverse;print for($,,$;,$*,$/)
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