Sorry my mistake, $data is a reference to an array-of-arrays rather than an array. Try this

my @count = map {$_->[0]} @$data;
my $code_retour = $oracle_connector->check_threshold(
  check    => \@count,
  warning  => $oracle_connector->opts->warning,
  critical => $oracle_connector->opts->critical,
);
$oracle_connector->plugin_exit($code_retour,"File attente (@count)" );
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