./script.pl "\t" ARG1 ARG2 

##</code><code>##

my $delim = shift @ARGV;
$" = $delim;
...
print "@list";

##</code><code>##

list_item1\tlist_item2\tlist_item3 

##</code><code>##

list_item1   list_item2    list_item3

##</code><code>##

$" = "\t"