Consider the following code:

local $_ = 'foo';
say 'Start' if /\G foo/gcx;
say 'Mid'   if /\G .*/gcx;
say 'End'   if /\G \z/gcx;

[download]

The output will be?

Start
Mid

[download]

Change the "Mid" case to this:

say 'Mid' if /\G .+/gcx;

[download]

And now the output will be:

Start
Mid
End

[download]

So all three conditions match. If you use the following quantifiers at the end of the 2nd expression, /z will not match in the third expression:*, ?, {0,}.

This is confirmed on Perl 5.26, and 5.10.

Similarly:

perl -E 'local $_ = "foo\n"; say "Start" if /\G foo/gcx; say "Mid" if 
+/\G .*/gcx; say "End" if /\G (?=\n)/gcx'

[download]

So in this case we added a \n to the string, matched on .* for our "Mid" expression. Then did a lookahead assertion for \n in the "End" expression. Since we are not using the /s modifier, .* should have stopped before \n, so (?=\n) should still find newline (I think), so the "End" condition should be true.

I'm feeling like the difference between how .+ and .* are consuming the string (/z matching in the 3rd expression when the 2nd expression uses .+, but not matching if .*) is an inconsistency that can't be defended as not being a bug, but I'm interested in what others take on it might be.


Dave

In reply to Seeking clarification on possible bug in regex using \G and /gc by davido

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