Finally after looking deeper I found another way to handle arrays and not using pack. Update: fastcmp optimized.

my @a = ("AAAA", "BBBB", "CCCCC");
print array_search(\@a,"B");


__END__
__C__
#include <stdio.h>
void hello_world() {
        printf ("Hello CDRs checkers!\n");
}
//s1 is the substring, s2 is the string
int fastcmp ( char *p1, char *p2 ) {
  int count = 0;
  while( *p1 ){
    char *a = p1, *b = p2;
    while( *a && *a == *b ) {a++;b++;}
    count += !*b;
    ++p1;
  }
  return count;
}

int array_search(AV *a1, SV *s1){
        STRLEN bytes1;
        char *p1;
        long a1_size,i;
        a1_size = av_len(a1);
        //printf ("%d\n",a1_size);
        //printf ("%s\n",SvPV_nolen (*elem));
        p1 = SvPV(s1,bytes1);
        for(i=0;i<=a1_size;++i){
        SV** elem = av_fetch(a1, i, 0);
        printf("%s %s\n",p1, SvPV_nolen (*elem));
            if (fastcmp(p1,SvPV_nolen (*elem)) > 0){
                return 1;
                }
        }
        return 0;
}
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This will produce :

B AAAA
String size: 1
Char at 0 is B = A
B BBBB
String size: 1
Char at 0 is B = B
1
[download]