my $foo = "bar";
sub bad_example { $_[0] =~ s/a/oo/; $_[0] }
print "\$foo: $foo\n";
print "bad_example returns: ", bad_example( $foo ), "\n";
print "uh oh, \$foo: $foo\n";

##</code><code>##

sub take_one_and_hash {
  my $one = shift;
  my %hash = @_;

  ## frobulate $one based on %hash . . .
}