$c = $a - $b;

##</code><code>##

... code ...
sub subtraction{
  chomp(@_ = split(" ", <STDIN>)); # user enters values on one line
  foreach(@_) {
    $result -= $_;    # I guess I am using the WRONG operator
  }
print "Result: $result\n\n";
... rest of subroutine code ...
}