Re: Flip-flop won't DWIM

[akho]

The /./ matches E, so flip-flop starts over.

[Roy Johnson]

So use the match-once operator (no need for an actual pattern; the empty pattern works fine):

print join ' ', grep scalar(??../D/), ('A'..'F');

[wu-lee]

Aha! Finally, a use for the match-once operator! And it seems to be tailor made for this problem. Bravo!

[akho]

Also: List::MoreUtils is your friend.

[wu-lee]

Yes. However, List::MoreUtils is not in core, so it's not something I want to rely on in the current circumstance.

[wu-lee]

Right. Of course, silly me.

Ok, so this does what I want:

perl -lwe '$x = 1; print join " ", grep { scalar($x++../D/) } qw(A B C
+ D E F)'
# prints:
# A B C D

Although this is not particularly neat. Is there a better way?

[akho]

Your code prints "A B C D E F" for me, and I cannot see why it would print anything else.

This seems to work if you insist on using flip-flop:

$x = 1; print join " ", grep { $x..(($x=0) or /D/) } qw(A B C D E F);

However, you could copy stuff from List::MoreUtils.

[wu-lee]

Actually, that doesn't, but this does:

 perl -lwe '$x = 0; print join " ", grep { scalar(!$x++../D/) } qw(A B
+ C D E F)'
 # prints:
 # A B C D

[ikegami]

The "++" does nothing.