my %name_of_id;

for my $id ( @all_ids )
{
    if ( ! exists $name_of_id{$id} )
    {
        my $name = get_name_of_id($id); # whatever

        $name_of_id{$id} = $name;
    }
}

##</code><code>##

$name_of_id{$_} ||= get_name_of_id($_)
    for @all_ids;