##
DB<41> $_="hello"; say pos,"($1)" while m/(o*$)/g; # pos doesn't change
5(o)
5()
DB<42> p "hello" =~ s/x*$/O/gr; # empty match (no x)
helloO
##
##
DB<44> p "hello\nfoo" =~ s/o*\n/O/gmr;
hellOfoo
DB<45> p "hello\nfoo\n" =~ s/o*\n/O/gmr; # added \n at the end of input
hellOfO
DB<46>
##
##
DB<59> p "12345" =~ s/x*/ /gmr;
1 2 3 4 5
DB<60>