{section name=customer loop=$custid}
	{$smarty.section.customer.index} id: {$custid[customer]}<br>
	{* FYI, $custid[customer.index] and $custid[customer] are identical in meaning *}
	{if $custid[customer.index_prev] ne $custid[customer.index]}
    	The customer id changed<br>
	{/if}
	{/section}


	OUTPUT:

	0 id: 1000<br>
    	The customer id changed<br>
	1 id: 1001<br>
    	The customer id changed<br>
	2 id: 1002<br>
    	The customer id changed<br>