$_ = 'bb ca de';
/(?:(.)b|.)+/i;
print "Test:             1='$1', 2='$2'\n";
# Prints:  Test:   1='e', 2=''
# vs
$_ = 'e';
/(?:(.)b|.)+/i;
print "Test:             1='$1', 2='$2'\n";
# Prints:  Test:   1='', 2=''

# BUT!
$_ = 'efg';
/(?:(.)b|.)+/i;
print "Test:             1='$1', 2='$2'\n";
# Prints:  Test:   1='', 2=''