Minimal fix (<= ⇒ <):

my $count = @{ $doc->{$sub1} };
for (my $i=0; $i<$count; $i++)
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Easier to read:

my $count = @{ $doc->{$sub1} };
for my $i ( 0 .. $count-1 )
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Alternative:

my $last = $#{ $doc->{$sub1} };
for my $i ( 0 .. $last )
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