open( my $fh, ">", $output ) or die_with_error();
####
my $value = $some_other_value || undef;
##
##
my $filename = $some_filename || default_filename();
##
##
my $filename = $some_filename ? $some_filename : default_filename();
##
##
# original
my $filename = prompt_for_filename() || default_filename();
# can't do this
my $filename = prompt_for_filename() ? prompt_for_filename()
: default_filename();
# coverage-happy version
my $prompted_filename = prompt_for_filename();
my $filename = $prompted_filename ? $prompted_filename
: default_filename();