while ( my $dir = shift @ARGV ) {
    my $dh = new DirHandle $dir;
    if ( defined($dh) ) {
        $dir =~ s/\/$//; # Here, for example...
        while ( defined($_ = $dh->read) ) {
            if ( $_ =~ /(\.csv)$/ ) {
                push @files, "$dir/$_";
            }
        }
    }
}