use Inline C;
print char_freq_diff_sum("123456", "abcdefghijkl"),"\n";

__DATA__
__C__
#define abs(x) (x<0?-x:x)   /* no need for math.h */

int char_freq_diff_sum(char *s, char *t) {
    int i, sum=0, freqs[256]={0};
    for(i=0; i<strlen(s); ++i) freqs[s[i]]++;
    for(i=0; i<strlen(t); ++i) freqs[t[i]]--;
    for(i=0; i<256; ++i) sum += abs(freqs[i]);
    return sum;
}