Re^2: Processing while reading in input

Thank you, tybalt89. Your code worked in terms of generating the expected output.

Could you please explain in detail the following 2 lines from your code? Thank you!

 
my ($cluster, $member) = split;
print $cluster eq $member ? "\n" x ($. > 1) : ', ', $member;
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Re^3: Processing while reading in input by AnomalousMonk (Archbishop) on Sep 20, 2018 at 03:47 UTC
Let me presume to answer for tybalt89. `my ($cluster, $member) = split;` This depends on default behavior of split, and is equivalent to `my ($cluster, $member) = split ' ', $_;` The `' '` split pattern is a special case explained in `split` docs. `print $cluster eq $member ? "\n" x ($. > 1) : ', ', $member;` This is a bit more tricksy. From the inside out: `($. > 1)` `$.` is input line counter (update: see perlvar). `($. > 1)` evaluates to either '' (empty string) or 1 and will be 1 for every input line after the first. `"\n" x ($. > 1)` Repeats a newline zero times for the first line of input (empty string silently promoted to 0 in this special case), once for every subsequent input line. `$cluster eq $member ? Newline_or_Nada : ', '` Ternary expression. If `$cluster eq $member` true, output newline for every input line after the first (see previous item); if false, output `', '` string. `print Ternary_Expression, $member;` print result of ternary expresssion (see previous item), then `$member` string. And that's all there is to it (I think). Update: Minor wording changes. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]

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Re^3: Processing while reading in input
by AnomalousMonk (Archbishop) on Sep 20, 2018 at 03:47 UTC

Let me presume to answer for tybalt89.

my ($cluster, $member) = split;

This depends on default behavior of split, and is equivalent to
my ($cluster, $member) = split ' ', $_;
The ' ' split pattern is a special case explained in split docs.

print $cluster eq $member ? "\n" x ($. > 1) : ', ', $member;

This is a bit more tricksy. From the inside out:

($. > 1) $. is input line counter (update: see perlvar). ($. > 1) evaluates to either '' (empty string) or 1 and will be 1 for every input line after the first.
"\n" x ($. > 1) Repeats a newline zero times for the first line of input (empty string silently promoted to 0 in this special case), once for every subsequent input line.
$cluster eq $member ? Newline_or_Nada : ', ' Ternary expression. If $cluster eq $member true, output newline for every input line after the first (see previous item); if false, output ', ' string.
print Ternary_Expression, $member; print result of ternary expresssion (see previous item), then $member string.

Update: Minor wording changes.

Give a man a fish: <%-{-{-{-<

[reply]
[d/l]
[select]