in reply to Re^3: how to read STDIN interactively
in thread how to read STDIN interactively

Okay, yes, I can see that's what it is doing - the second time it returns EOF.

But I don't understand why then, if I am reading a line at a time, ($/ = \n) I don't have to read twice - once to read the chunk, and once to read the newline.

Also, why doesn't it work in the case when I made $/ local and undefined it in its own namespace, and the other case where I set $/ back to a newline immediately after the read.

I agree, reading it in list context is the simplest way, but I'd like to understand what is going on.

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Re^5: how to read STDIN interactively
by ikegami (Patriarch) on Feb 25, 2011 at 01:47 UTC

    The undef being returned isn't the value of $/, it's a signal that EOF was reached.

    Your are mistaken about the behaviour being different when $/ eq "\n". It doesn't matter what $/ is. If you only have one line, the second read will be undef. 

    $ echo "abc" | perl -E'$/ = undef; say defined(<>)||0 for 1..2;'
1
0

$ echo "abc" | perl -E'$/ = "\n"; say defined(<>)||0 for 1..2;'
1
0

    [download]

    You saw a difference in your tests because you passed two lines before EOF with $/ eq "\n", but only one line before EOF with !defined($/).

    By the way, relying on the user to close STDIN between inputs creates a stinky interface.

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      It looks like I am lacking some needed basic prerequisite stuff to understand what you all are talking about. I'm gonna need to do some studying.

      thanks much.
[reply]
        Think of what it takes to stop while (<>) (which is short for while (defined($_ = <>))).
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