As to whether or not the comma operator is more readable in this situation, I leave that to the reader(s) to decide. My C background enables me to easily understand this construct, but many folks here may not find that "readable".

I think we are "drilling way down into the dirt here". The main point that is important here is testing of eof instead of !defined. I personally declare this thread a "success". Been "beat to death" and a definite, informative, high-performance, clear answer has been arrived at.

I share your doubts about using comma in void context to separate commands like semicolon does, I only do it in exceptional cases.

OTOH it's not too different of comma's behavior in list context

 print sqrt($i), $i, $i**2;

just without returning the results.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!}

Geez, ok, round #n

The use of comma in your print statement works exactly the same.
Consider:

#!/usr/bin/perl
use strict;
use warnings;

my $i = 3;

# $i is not modified in this print statement:

print sqrt($i), $i, $i**2; #  1.7320508075688839
                           ## 1.73205080756888  3  9
                           
# $i is modified and new value of $i is used:

print sqrt($i), --$i, $i**2; #  1.7320508075688824
                             ## 1.73205080756888  2  4
[download]

I like the comma statement when it simplifies a loop, an example is a loop that prompts for an input:

#!/usr/bin/perl
use strict;
use warnings;

my $line;

while ( (print "Prompt: "), $line=<STDIN>, $line !~ /^\s*Q(uit)\s*$/i 
+)
{
   $line =~ s/^\s*//;
   $line =~ s/\s*$//;
   
   print"xyzzy \"$line\" and nothing happens\n";
}

print "Some version of QUIT, QuIt, quit entered\n";

__END__
C:\Projects_Perl\testing>perl simplecommandline.pl
Prompt:    123
xyzzy "123" and nothing happens
Prompt: abc
xyzzy "abc" and nothing happens
Prompt:   123 abc
xyzzy "123 abc" and nothing happens
Prompt: qui
xyzzy "qui" and nothing happens
Prompt: quit doing that!
xyzzy "quit doing that!" and nothing happens
Prompt: QUiT
Some version of QUIT, QuIt, quit entered
[download]

Without the use of the comma statement in the while() statement, there has to be a "prompt" printed before the loop starts and a "prompt" must also be printed within the loop to "keep the loop going". The comma statement allows: a)ask for input, b)get input, c)test input all in one syntactically correct single statement. The "truthfulness" of a comma statement only rests upon the very last clause. This comma statement idea should be used sparingly. Very sparingly. I think we agree upon that.