Re: Is there a reason to use "join" instead of just using the period?

[BrowserUk]

Perhaps he didn't know about the ${varname} technique and had trouble with the underscores.

Personally, I like your last one best. Though I'd use single quotes for constant bits.

Mind you, if you remove the redundant double quote from his variables, that looks a lot less busy:

$hotfix = join '', $app, '_', $mod, '_', $bld, '_', $hf, '.zip';