print "$date_a\n$date_b\n";
print "Do these dates differ by more than 72 hours? ";
my $ans = <>;

my $differ_by_more_than_72;
if( $ans =~ /[Yy][Ee][Ss]/ ) {
  $differ_by_more_than_72 = 1;
} else {
  $differ_by_more_than_72 = 0;
}