use v5.20; # use warnings and strict. Makes "say" available

sub add( $ _ ) # Two scalars, the second is $_ if not provided
{
  $_ = $_[0] + $_[1];
}

sub ans
{
  $_
}

$_ = 7 and say;

add 4, 5 and say; # prints 9
add 2 and say;    # prints 11
add -4 and say "The answer is: ", ans; # prints 7