$_ = 'abc';

while (/
   ( (?=.) )
   (?{ printf("pos=%d len=%d\n", pos($_), length($1)); })
/xg) {
   print("Match\n");
}
print("\n");

while (/
   ( . )
   (?{ printf("pos=%d len=%d\n", pos($_), length($1)); })
/xg) {
   print("Match\n");
}