Perl puzzle of the week/month/year

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August 10th, 2009, 01:04 PM

Scorpions4ever

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Perl puzzle of the week/month/year

As promised, here's the new perl puzzle of the week/month/year. This one is short and sweet.

perl Code:

Original - perl Code
#!/usr/bin/perl –aw use strict; my $x = 23; my $y = 42; my $z = 69; $a = ($x + $y) * $z; print “a = $a\n”;

 
#!/usr/bin/perl –aw
use strict;
 
my $x = 23;
my $y = 42;
my $z = 69;
 
$a = ($x + $y) * $z;
print “a = $a\n”;

The question here is why does this code run fine, in spite of the use strict; directive?

As before, usual rules apply:
* I will post the solution on friday, if no one else has got it by then.
* First person/people to post the correct answer will have their names on my signature for a while (until I post the next puzzle)
* Judge's discretion is final
* Keep on truckin'

Comments on this post

ishnid agrees: Puzzles are fun. More, more!

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Puzzle of the Month solved by Fishmonger, superior perl programmer of the month

Last edited by Scorpions4ever : August 10th, 2009 at 01:08 PM.

August 10th, 2009, 01:25 PM

FishMonger

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$a as well as $b are built-in global vars that are used in sorting and while using them outside of a sort routine is allowed, it's discouraged.

EDIT: maybe I should post the related documentation from perldoc perlvar

Quote:

# $a
# $b

Special package variables when using sort(), see sort. Because of this specialness $a and $b don't need to be declared (using use vars, or our()) even when using the strict 'vars' pragma. Don't lexicalize them with my $a or my $b if you want to be able to use them in the sort() comparison block or function.

Last edited by FishMonger : August 10th, 2009 at 01:33 PM.

August 10th, 2009, 02:01 PM

KevinADC

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My answer would have been the same as FishMongers. Not sure why you have the -a switch on the shebang line. Might confuse some people trying to answer the question(s) thinking it somehow makes the code fly.

August 11th, 2009, 02:49 PM

Scorpions4ever

Banned ;)

Join Date: Nov 2001

Location: Glendale, Los Angeles County, California, USA

Posts: 8,344

Time spent in forums: 1 Month 1 Week 4 Days 13 h 47 m 33 sec
Reputation Power: 2532

Fishmonger: That was the correct answer

KevinADC: The -a was a red herring. Originally when I posted the puzzle in my office, I was messing with another predefined var that gets activated with -a, but it didn't work right.

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