Hello AnomalousMonk, and thanks for the writeup.

Is your Supplemental question meant rhetorically? Because I, for one, would really like to know the answer! Consider the following:

19:40 >perl -wE "my $s = 'abCdefC'; while ($s =~ / (f)*? C /gx) { say 
+qq[match: $1, pos = ], pos $s; }"
Use of uninitialized value $1 in concatenation (.) or string at -e lin
+e 1.
match: , pos = 3
match: f, pos = 7

19:41 >

[download]

In this case the regex engine does not say: “Well, matching 1 f is better than matching none, so I’ll match the fC sequence first.” On the contrary, it first matches the C preceded by zero fs, as one might reasonably expect from the quantifier, *?, which says, “match this zero or more times in a non-greedy way.” I actually don’t understand how this can ever, logically, match with more than zero, since zero is possible and less greedy than 1??

But back to the OP, how does $dna =~ / (\w\w\w)*? TGA /gx differ logically from $s =~ / (f)*? C /gx? I can’t see a fundamental distinction here, yet there must be one because the former finds a non-empty match for (\w\w\w) before it looks for an empty one!

Thanks,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re^7: Understanding a portion of perlretut by Athanasius
in thread Understanding a portion on the Perlretut by BlueStarry

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