$a = "12||23||34||45";

@a = split("\|\|", $a);
print join(",", @a);

##</code><code>##

12,23,34,45

##</code><code>##

1,2,|,|,2,3,|,|,3,4,|,|,4,5

##</code><code>##

$a = "12||23||34||45";

@a = split(/\|\|/, $a);
print join(",", @a);

##</code><code>##

$a = "12||23||34||45";

@a = split("\\|\\|", $a);
print join(",", @a);