Re: Modulus by zero?

Now that is interesting…

>perl -MO=Deparse -e "$a if $b %% 5 == 0"
$a if $b % %5 == 0;
-e syntax OK
[download]

So %5 is some sort of hash!?

From perlvar

Perl variable names may also be a sequence of digits or a single punctuation or control character. These names are all reserved for special uses by Perl; for example, the all-digits names are used to hold data captured by backreferences after a regular expression match.

So the scalar variant of those digit vars are well-known, but the hash variant is "reserved" and serves no special purpose by now.

Comment on Re: Modulus by zero? Select or Download Code

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Re^2: Modulus by zero? by shmem (Chancellor) on Nov 17, 2006 at 15:11 UTC
The documentation is somewhat misleading at this point. Only all-digit scalars are read-only backreferences to captures, while all-digit hashes and arrays are not, not even read-only. But yes, they might be reserved :-) `perl -le '@2 = 1..3; @1{qw(a b c)} = @2; print "$_=>$1{$_}" for keys % +1' c=>3 a=>1 b=>2` [download] Use of @1, %2 and so on is a common obfuscation technique. --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l]
Re^2: Modulus by zero? by ikegami (Patriarch) on Nov 17, 2006 at 17:22 UTC
Also interesting is how the variable doesn't need to be declared, since it is automatically considered a package variable. `>perl -Mstrict -e "@1 >perl -Mstrict -e "my @1 an't use global @1 in "my" at -e line 1, near "my @1" Execution of -e aborted due to compilation errors.` [download] Update: Ah, other special-like variables are like that too. `>perl -Mstrict -e "%! >perl -Mstrict -e "my %! Can't use global %! in "my" at -e line 1, near "my %!" Execution of -e aborted due to compilation errors.` [download]	[reply] [d/l] [select]
Re^2: Modulus by zero? by orderthruchaos (Scribe) on Nov 17, 2006 at 14:11 UTC
IGNORE THIS I think it may be interpreting it as `$b % undef % 5 == 0;` undef would then be converted to zero before processing.	[reply] [d/l]
Re^3: Modulus by zero? by Fletch (Bishop) on Nov 17, 2006 at 14:22 UTC
The `-p` option to B::Deparse can be helpful when precedence questions arise: `$ perl -MO=Deparse,-p -e '$a if $b %% 5 == 0' ((($b % %5) == 0) and $a); -e syntax OK` [download]	[reply] [d/l]
Re^3: Modulus by zero? by orderthruchaos (Scribe) on Nov 17, 2006 at 14:17 UTC
Oops... nevermind... you're right... From the perl DB: `DB<2> x \%5 + 0 HASH(0x500be0) empty hash` [download]	[reply] [d/l]