"\n" =~ /\n.*\z/;   # matches

##</code><code>##

"\n" =~ /.*\z/;     # doesn't match. i would expect it to match

##</code><code>##

"\n" =~ /[^\n]*\z/; # matches. like expected. but [\n]* is like .*

##</code><code>##

"\n" =~ /.?\z/;

##</code><code>##

"\n" =~ /.{0,}\z/;

##</code><code>##

"f\n" =~ /.?f\z/;