while ('abc' =~ /(.)/g) {
   print($1);
}

##</code><code>##

while ('abc' =~ /(?=(.))/g) {
   print($1);
}

##</code><code>##

$_ = '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");
}

##</code><code>##

pos=0 len=0
Match
pos=0 len=0   # Same pos & len as last pass -> No match.
pos=1 len=0
Match
pos=1 len=0   # Same pos & len as last pass -> No match.
pos=2 len=0
Match
pos=2 len=0   # Same pos & len as last pass -> No match.

pos=1 len=1
Match
pos=2 len=1
Match
pos=3 len=1
Match