use Cwd;

sub process_files {
    my $path = shift;
    my $dir = getcwd;
    chdir( $path ) or die "chdir($path) failed: $!";

    opendir (my $dh, ".") or die "Unable to open ".": $!\n";
    my @files = grep { !/^\.\.?$/ } readdir ($dh);
    closedir ($dh);

    foreach(@files){
      if ( -d $_ ) {
         process_files($_);
      }
      elsif ( $_ =~ /\.pdw$/ ) {
         push @files_erg, $_;
      }
    }      
    chdir ( $dir ) or die "chdir($dir) failed: $!\n";
}