Why is this a symbolic reference?

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

Hi, I want to use something like this in a script of mine :

print keys %{ hash_ref -> { key } }; #( Hash of Hash )
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But when I try to execute this with 'strict' on, I get an error telling me that this is a symbolic reference.
Seems I haven't really understood what a sym ref is because I always thought that that would be something like this :

print keys %{ hash_ref -> { "key" } }; #( Hash of Hash )
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print keys %{ "hash_ref -> { key }" }; #( Hash of Hash )
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How should I rewrite my first line to make it work with 'strict' turned on. Thanks.

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Re: Why is this a symbolic reference? by btrott (Parson) on Mar 05, 2001 at 00:08 UTC
You're missing a $. Your code should look like this: `print keys %{ $hash_ref -> { key } };` [download] The symbolic reference error comes from your code trying to dereference a string: `hash_ref->{key}` [download] hash_ref isn't a hash ref, it's a string. $hash_ref is the hash ref.	[reply] [d/l] [select]
Re: Why is this a symbolic reference? by japhy (Canon) on Mar 05, 2001 at 00:09 UTC
It's a symbolic reference because you're doing: `hash_ref->{key}`, which is like `"hash_ref"->{key}`, which is ending up being `$hash_ref{key}`, but in a round-about way. Perhaps you meant `$hash_ref->{key}`. `japhy` -- Perl and Regex Hacker	[reply]
Re (tilly) 1: Why is this a symbolic reference? by tilly (Archbishop) on Mar 05, 2001 at 02:21 UTC
Even if you put the dollar signs in, your placement of quotes in the second version would make it a symbolic reference. And in the first version it might arise still if some of the values in %hash_ref are not hashes. (That is the kind of error that can be very, very hard to track down without strict on.) Still try this: `print keys %{ $hash_ref->{$key} };` [download] and it will work as long as your data structure is what you think it is. BTW for inspecting a data structure I usually use Data::Dumper.	[reply] [d/l]