endless loop while .=

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Fellow Monks, consider the following code

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

my $content;

open(IN, "<", $ARGV[0]) or die $!;
while ( $content .= <IN> ) {
  print $content;
};
close(IN) or die $!;
[download]

Can someone explain in laymans words why .= causes an endless while loop?

Comment on endless loop while .= Download Code

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Re: endless loop while .= by almut (Canon) on Jan 23, 2010 at 13:28 UTC
...because `$content` is accumulating the input. In other words, it isn't empty/false when the while loop has reached the end of the input, so the while loop keeps running.	[reply] [d/l]
Re^2: endless loop while .= by Anonymous Monk on Jan 23, 2010 at 13:39 UTC
Thank you.	[reply]
Re: endless loop while .= by Marshall (Canon) on Jan 23, 2010 at 13:42 UTC
See explanation by almut - while() is testing true/false of the statement, not status of <IN>. Here is small mod to your code that avoids the problem. `#!/usr/bin/perl use warnings; use strict; my $content; open(IN, "<", $ARGV[0]) or die $!; while ( <IN> ) { print $content.= $_; }; close(IN) or die $!;` [download]	[reply] [d/l]
Re: endless loop while .= by apl (Monsignor) on Jan 23, 2010 at 13:26 UTC
You can always append a Null ...	[reply]