As Hugo van der Sande wrote less than a week ago, regexes execute their alternations in the order you provide them. Thus, the "a" alternation is attempted before the "ab" one.
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Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re: Greedy regexp matching: differences between man page and implementation? by japhy
in thread Greedy regexp matching: differences between man page and implementation? by stijnvs

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