my %hash_one = ('string_one' => 0, 
                                                'string_two' => 0, 
                                                'string_three' => 0, 
                                                'string_four' => 0, 
                                                'string_five' => 0, 
                                                'string_six' => 0, 
                                                'string_seven' => 0);
# first, create an array ref, element 0 is a qr// of the key, and element 1 is the count:
for (keys %hash_one) {
  $hash_one{$_} = [qr/$_/, 0];
}
# then walk the data, trying all the regexen:
@ARGV = qw(file.txt);
close ARGV;
while (<>) {
  for (keys %hash_one) {
    $hash_one{$_}[1]++ if qr/$hash_one{$_}[0]/;
  }
}
# finally, replace the arrayref with just the count:
$_ = $_->[1] for values %hash_one; # works in perl 5.5 and greater