my $dir = '/Path/to/a/data/directory';

opendir my $DH, $dir or die "Cannot open '$dir' $!";

my %hash;
while ( my $file = readdir $DH ) {

    next if $file =~ /~$/;
    next if -d "$dir/$file";                       # should also skip '.' and '..' entries

    # read and process file
}