PowerShell Script to Copy Members of One Group to Another

#Author: Kim Doan
#Please tell me this code suck so that I can improve

# Adding Prerequisite Active Directory Module
if ( !(get-module -name "ActiveDirectory") ) {"ActiveDirectory module not in shell environment. Now importing..."; Add-WindowsFeature RSAT-AD-PowerShell; import-module -name "ActiveDirectory" -DisableNameChecking | out-null }

Do{
$fromGroup = Read-Host -Prompt 'Copy From Group:'
$toGroup =  Read-Host -Prompt 'Copy To Group:'

# This convoluted code is to be backward compatible with older PowerShell versions
$oldMembers=(Get-ADGroupMember -Identity $fromGroup -Recursive);
$newMembers=(Get-ADGroupMember -Identity $toGroup -Recursive);
$old=@();
$new=@();
$index=0;

foreach ($newMember in $newMembers){$new+=,$newMember.name}
foreach ($oldMember in $oldMembers){$old+=,$oldMember.name}

foreach ($o in $old){
if ($new -contains $o){#Do nothing#"$o already exists at the destination";}
else {
Add-ADGroupMember -Identity $toGroup -Members $oldMembers[$index];
"New entry '$o' from '$fromGroup' has been copied to the group '$toGroup'";
}
$index+=1;
}

$flag = Read-Host -Prompt 'Press Any Key = exit; C = Continue Copying...'} while ($flag -match '[Cc]')