Yeah, the half-pair is fun. Personally I would have split up that re as:

$s =~ s>{.*?}
       >{$sub[$n++]}
       >gx;
[download]

...but TIMTOWTDI. And as for the pipe being the character for alternation... you're right of course. But not many characters are used infrequently enough that they make good delimiters. So I just use whichever I feel looks good until there's a conflict with the content of the regex.

LAI