backticks/escapeHTML strange behaviour with assignment

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

Could someone explain to me why the following code depends on whether the value is assigned to a variable or not?

use CGI 'escapeHTML';

print "\n--- take 1 ---\n";
print escapeHTML(`echo abc; echo def; echo ghi`);

print "\n--- take 2 ---\n";
print escapeHTML($b = `echo abc; echo def; echo ghi`);

print "\n--- take 3 ---\n";
$c = `echo abc; echo def; echo ghi`;
print escapeHTML($c);
[download]

When I run this, I get:

--- take 1 ---
abc&#10;
--- take 2 ---
abc
def
ghi

--- take 3 ---
abc
def
ghi
[download]

Tested on:

perl 5.14.2 under Ubuntu 12.04 x86_64
perl 5.12.3 under OSX 10.7.5

Comment on backticks/escapeHTML strange behaviour with assignment Select or Download Code

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Re: backticks/escapeHTML strange behaviour with assignment by candlerb (Novice) on Nov 29, 2013 at 08:46 UTC
I found it. man perlop for backticks: "In scalar context, a single string consisting of all output is returned. In list context, a list of values is returned, one per line of output." Solution: print escapeHTML(scalar(`echo abc; echo def; echo ghi`)); [download]	[reply] [d/l]
Re: backticks/escapeHTML strange behaviour with assignment by boftx (Deacon) on Nov 29, 2013 at 08:47 UTC
The only thing I can think of right off the top is that without the assignment in Take 1 the newlines are preventing more than the first "echo" from being seen by `escapeHTML`. It helps to remember that the primary goal is to drain the swamp even when you are hip-deep in alligators.	[reply] [d/l]