#!/usr/local/ActivePerl-5.16/bin/perl

use POSIX qw/strftime/;


sub fixdir {
    my $dir = shift;
    opendir my $DH, $dir or die "Not Found....$dir: $!";
    while (my $f = readdir $DH) {
        next if grep $_ eq $f, qw/. ../;
        (my $new = $f) =~ s/[^a-zA-Z0-9_.]/_/g;
		next if ($new eq $f);
		while ( -e "$dir/$new") { $new .= "1";  }
        print STDERR "Renaming: $f -> $new\n";
        rename "$dir/$f", "$dir/$new";
        fixdir("$dir/$new") if -d "$dir/$new";
    }
}


$Do_Dir = @ARGV[0];
print("ARG=", "$Do_Dir", "<<<<<<\n");
if ("$Do_Dir" == null ) {
	print ("No Folder Name given!\n");
	exit; }
print( "The Folder Name is: ", "$Do_Dir", "\n" );
fixdir($Do_Dir);
print "Done..."

produces this....
9858-215-rfleisch:test_it p00015282$ ./Change_FName2.pl these
ARG=these<<<<<<
No Folder Name given!
9858-215-rfleisch:test_it p00015282$ ./Change_FName2.pl
ARG=<<<<<<
No Folder Name given!
9858-215-rfleisch:test_it p00015282$ 

Notice the SAME results ????????