my @files = glob("./*");
for my $filename (@files) {
    (my $newname = $filename ) =~ s/[^A-Za-z0-9\.]/_/;
    if ( -e $newname ) {
        warn "$newname already exists, skipping rename on $filename\n";
    }
    else {
        rename $filename, $newname;
    }
}

##</code><code>##

perl -pi.bak -e 's/[^\w\.\t \n]//' <files>