不能将字符串（“ 1”）用作HASH引用，嵌入式哈希问题

Question

Many similar questions have been asked, but mine is quite specific and none of the answers seem to work.

The script below is run in a loop (over @keys ). I want to check if some pattern is available as a value (second if ). If it is, get the ending number out of it. Then, I want to add a value on the index of that number in an array that does not necessarily exist yet. The example input/output below might clarify things.

The reference might be a bit complicated, but it is the idea that %ini is a hash, bf in there is a hash, and another one in there eg topattrs . Finally, in the next element $v I want to create an array alts if it doesn't exist yet. It has to be an array and not a hash because the order of this array matters! Then, I want to add the value of $alt on that index position.

my @keys = keys %{$ini{'bf'}};
foreach (@keys) {
    my $v = $ini{'bf'}{$_};
    if (my ($p, $d) = $_ =~ /(top|sub)attr(\d+)$/) {
        $ini{'bf'}{"${p}attrs"}{$v} = 1;
        delete $ini{'bf'}{$_};

        if (my ($alt) = grep( /${p}attr${d}_alt\d+/, @keys ) ) {
            my ($altd) = $alt =~ /(\d+)$/;
            $ini{'bf'}{"${p}attrs"}{$v}{'alts'}[$altd] = $ini{'bf'}{$alt}; # line 23
        }
    }
}
print Dumper(\%ini);

However, Perl throws me an error:

Can't use string ("1") as a HASH ref while "strict refs" in use at line 23.

So I guess Perl is interpreting alts as a hash, even though I want to use it as an array so I must be doing something wrong when referencing. Maybe the fact that the array doesn't exist beforehand has to do with it as well?

Example input:

$VAR1 = {
  'bf' => {
    'subattr2_alt2' => 'pos',
    'subattr2_alt1' => 'pt',
    'topattr1' => 'cat',
    'subattr1' => 'rel',
    'subattr2' => 'cat'
  }
};

Output wanted:

$VAR1 = {
  'bf' => {
    'topattrs' => {
      'cat' => 1
    },
    'subattrs' => {
      'cat' => ['pt', 'pos'],
      'rel' => 1
    }
  }

Answer 1

You set the $ini{'bf'}{"${p}attrs"}{$v} to 1 and then later on (line 23) try to use the same as a hash.

my @keys = keys %{$ini{'bf'}};
foreach (@keys) {
    my $v = $ini{'bf'}{$_};
    if (my ($p, $d) = $_ =~ /(top|sub)attr(\d+)$/) {
        $ini{'bf'}{"${p}attrs"}{$v} = 1;       #### <==== HERE
        delete $ini{'bf'}{$_};

        if (my ($alt) = grep( /${p}attr${d}_alt\d+/, @keys ) ) {
            my ($altd) = $alt =~ /(\d+)$/;
            $ini{'bf'}{"${p}attrs"}{$v}{'alts'}[$altd] = $ini{'bf'}{$alt}; # line 23
        }
    }
}
print Dumper(\%ini);

Change the marked line to

$ini{'bf'}{"${p}attrs"}{$v} = {} ;

or simply remove the line because perl will create needed hashref due to autovivification.