Using a stored condition

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

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Re: Using a stored condition by jettero (Monsignor) on Mar 02, 2008 at 21:40 UTC
You could try any of these: `my $method1 = '(($a && $b)) \|\| ($c && $d)'; my $method2 = sub { my ($a,$b,$c,$d) = @_; (( $a && $b )) \|\| ($c && $d +) }; }; sub method3 { ... } print "yeah\n" if eval $method1; die $@ if $@; print "yeah\n" if $method2->($a,$b,$c,$d); print "yeah\n" if method3(...);` [download] -Paul	[reply] [d/l]
Re^2: Using a stored condition by legend (Sexton) on Mar 02, 2008 at 22:40 UTC
Thanks. It says: `Global symbol "$c" requires explicit package name at script.pl line 41 +. Global symbol "$d" requires explicit package name at script.pl line 41 +. Execution of script.pl aborted due to compilation errors.` [download] Any idea on what could be wrong?	[reply] [d/l]
Re^3: Using a stored condition by shmem (Chancellor) on Mar 02, 2008 at 22:55 UTC
I guess it's a line like `print "yeah\n" if $method2->($a,$b,$c,$d);` [download] in some scope where $c and $c aren't previously declared. Declare them with my. In case you wonder why $a and $b are missing from perl's complaint: Those variables are special. They are used in sort functions, so they exist anyways. It is discouraged to use them for any other purpose. See perlvar. --shmem _($_=" "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^4: Using a stored condition by legend (Sexton) on Mar 02, 2008 at 23:13 UTC
Re^5: Using a stored condition by shmem (Chancellor) on Mar 02, 2008 at 23:44 UTC
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Re^4: Using a stored condition by legend (Sexton) on Mar 02, 2008 at 23:22 UTC
Re^5: Using a stored condition by TGI (Parson) on Mar 03, 2008 at 00:43 UTC
Re^5: Using a stored condition by shmem (Chancellor) on Mar 02, 2008 at 23:50 UTC
Re^5: Using a stored condition by jettero (Monsignor) on Mar 02, 2008 at 23:45 UTC
Re^3: Using a stored condition by grizzley (Chaplain) on Mar 03, 2008 at 08:53 UTC
Because non of variables $a, $b, $c, $d was declared. The question is why $a and $b do not cause problems? The answer: because they are special variables used in sort function. And it is safer not to use them in sample codes because you can get results far from expected.	[reply]