the strange declaration with our, my and local is here.

declarations.pl

use feature qw(say);

use strict;
use warnings;

package Some;

our $n = 100;

sub say_n {
    say $Some::n;
}

say_n();

{
    for ( local $n = 0; $n < 10; $n++ ) {
        say_n();
    }
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    say '---';

    for ( my $n = 0; $n < 10; $n++ ) {
        say_n();
    }
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    say '---';
    say_n();
}

say_n();
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