The value you are retrieving from $decoded2->{HasAttachments} needs to be treated as a true or false value in your code - it does not need further decoding:

use JSON;
use Data::Dumper;

my $json = encode_json( {HasAttachments => \0} ); # \0 is JSON false
my $decoded = decode_json( $json );
print Dumper( $decoded->{HasAttachments} );

if ( $decoded->{HasAttachments} ) {
    print "HasAttachments is true";
}
else {
    print "HasAttachments is false";
}

# Prints:

$VAR1 = bless( do{\(my $o = 0)}, 'JSON::PP::Boolean' );
HasAttachments is false
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