print (4+5)*20;  # Prints 9, returns 20
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Yes, but at least that gets caught with warnings (or -w):

$ perl -we 'print (4+5)*20;'
print (...) interpreted as function at -e line 1.
Useless use of multiplication (*) in void context at -e line 1.
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The whitespace bug described in the original node is the first bug I've had in a while that:

• wasn't caught by syntax checking (it's valid Perl)
• wasn't griped about with strict and warnings on
• wasn't a design error
<–radiant.matrix–>
Ramblings and references
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet

Well, it's kind of you to say that, but given the fact that Perl 6 changed =~ to ~~, it arguably was a design error. (Though this particular failure mode is not why it was changed, but rather the failure of reversing the operator to say ~= instead. It doesn't matter if you reverse ~~.) Anyway, if you split ~~ in Perl 6 with whitespace, it'll parse, but will likely give you a "useless use of ~ in void context" warning.

By the way, Perl 6 also fixes the "print (4+5)*20" faq...

The whitespace bug described in the original node is the first bug I've had in a while that:

• wasn't caught by syntax checking (it's valid Perl)
• wasn't griped about with strict and warnings on
• wasn't a design error

I've got one of those, though not a whitespace bug. Just recently I was messing with a data-structure that was supposed to be an array of arrays of arrays:

$rect_list = 
  [  [ [0, 0], [3, 9 ] ],
     [ [5, 4], [3, 10] ], 
     [ [7, 8], [9, 11] ]. 
     [ [2, 4], [5, 15] ], 
     [ [1, 9], [9, 13] ], 
   ];
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First question: Can you spot the bug? Second question: Do you know what it does?

Did you know that <$x> is a readline, but <$ x> is a glob?

The lesson? I probably should have used Text::Trim. :)

It could be, but I would say the lesson is to not try to do it all in one step. I remember reading a Randal Schwartz rant some time back about people continually trying to do whitespace trimming in one step, when it's much simpler and straight-forward to do it in two:

$user =~ s/^\s+//s;
$user =~ s/\s+$//s;
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I think you'll find that that runs much faster than one regexp involving alternation....

Well, I don't really care much about faster runtimes -- most of what I do waits on disk access and network I/O long before it runs into RAM or CPU limits, so which regex is fastest almost never comes into play.

I try to write primarily for readability. I realize, of course, that "readability" is subjective. But, I find s{^\s+|\s+$}{}g to be more readable than the two-line alternative. When I see that one line, I immediately think "ok, trim whitespace from the ends". When I see the two, I have to stop and think about it. Just me.

One of the things I like about Python¹ is the readability of performing this action:

text = " a string of some sort, with space at either end   "
text = text.strip()
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I think that's what draws me to Text::Trim (if I have to do the step repeatedly, especially):

my $text = " a string of some sort, with space at either end   ";
$text = trim( $text );
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Of course, creating a dependency for something like that seems a little excessive, so I've recently taken to

my $TRIM_WHITESPACE_RE = qr/^\s+|\s+$/
## ... later on .. ##
$text =~ s/$TRIME_WHITESPACE_RE//g;
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1: I know, I know. :) Seriously, though, Python has some nifty things in it, even if I still like Perl better.

<–radiant.matrix–>
Ramblings and references
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet