DB<32> p "hello" =~ s/o*$/O/gr;
hellOO
  DB<33> $_="hello"; s/o*$/O/g; print       # for older Perls
hellOO
  DB<34>

##</code><code>##

  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

##</code><code>##

  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>

##</code><code>##

  DB<59> p "12345" =~ s/x*/ /gmr;
 1 2 3 4 5
  DB<60>