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RE: RE: RE: undefs and functions

by perlmonkey (Hermit)
on Aug 02, 2000 at 21:32 UTC ( #25790=note: print w/replies, xml ) Need Help??

in reply to RE: RE: undefs and functions
in thread undefs and functions

I maybe barking up the wrong tree, but I think I got your error. It took a bit of rooting around. Normally if the scalar is just a normal hash it should autovivify. Here is an autovivification example:
my $foo = { }; $foo->{a}->{b}->{c}->{d} = 1; use Data::Dumper; print Data::Dumper->Dump([$foo],['foo']);
$foo = { 'a' => { 'b' => { 'c' => { 'd' => 1 } } } };
All those keys were undef, but now they were created just by asking for them.

I got your error only when I tried to turn an undef into a hash reference explicitly:print %{$foo->{a}->{d}}
So maybe making it into a two step process:
my $bar = $foo->{a}->{d}; print %$bar if $bar;
that might take care of your errors. If I totally missed your problem, sorry.

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[hippo]: For explanation, I've seen this construct in someone else's code (no names, no pack drill) and couldn't think of a situation to trigger it.
[Corion]: You'll have to look somewhere esoteric for that. Maybe some tied variable or special dualvar can also trigger that. But it's certainly not a common occurrence
[Corion]: And on 5.20, the following also outputs no find:perl -wle 'for my $x ("\x{2000}".."\ x{1fffff}") { if( $x && ! length $x ) { warn qq(<$x>); warn length $x; die } }'
[Corion]: (this time on Unix)
[hippo]: Understood. I'll have to go through the code and see if it's doing anything fancy with ties, dual-vars or non-scalars. In the end, it's probably a bug though.
[Corion]: Aaah - you should be able to do this with overload, but I would hit somebody really hard if they constructed objects that are true but the empty string, and you not knowing about the domain knowledge where this makes sense

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