$string = 'hello, world'
$string = $string.replace('he','a')
$string = $string.replace('ll','m')
$string = $string.replace('o,','s')
$string = $string.replace(' ','i')
$string = $string.replace('wo','.d')
$string = $string.replace('rld','ll')

$string2 = 'hello, world'
$string2 = $string2.replace('he','A')
$string2 = $string2.replace('ll','m')
$string2 = $string2.replace('o,','s')
$string2 = $string2.replace(' ','i')
$string2 = $string2.replace('wo','Sc')
$string2 = $string2.replace('rld','an')

$string3 = 'hello, world'
$string3 = $string3.replace('hello','Bu')
$string3 = $string3.replace(', ','ff')
$string3 = $string3.replace('world','er')

$string