How to add comma separator after each string getting printed through foreach loops in smarty?

Question

I've following logic to print strings. Now the strings are getting printed but they are not separated by comma. I want to insert comma separator after each string printed. The comma should not get printed ater last string. How to achieve this? I tried almost every thing but not getting the desired result. So can someone who has good command over smarty help me in this regard? Thanks in advance.

{foreach from=$all_states item=state key='key'}
  {foreach from=$preview_data.applicable_states item=pre key='index'}    
    {if $state.id == $pre} {$state.state_name} {/if}
  {/foreach}  
{/foreach}

Answer 1

Another way to look at the problem is that a comma should be printed before every string except the 1st one, so create a variable called "comma" and initialize it to the empty string and set it to "," after the first string is printed.

Not tested but you get the idea:

{assign var="comma" value=""}
{foreach from=$all_states item=state key='key'}
  {foreach from=$preview_data.applicable_states item=pre key='index'}    
    {if $state.id == $pre} {$comma}{$state.state_name} {assign var="comma" value=","}{/if}
  {/foreach}  
{/foreach}