===
$default_str = "good food";
$string1 = $default_string;

$string2 = $default_string;

$string3 = $default_string;

$string1 =~ s/o*/e/;
print $string1;

$string2 =~ s/o+/e/;

$string3 = ~ s/o/e/g;

print $string1;
print $string2;
print $string3;

====