-w and use strict :)
$string probably isn't the best name for your variable and if the directory part is used elsewhere it is probably better as a seperate variable as well.
so try constructing your string like this

my $dir= 'c:/inetpub/vcaserver/miniV/section';
$html_file = $dir . $in{'pSection'} . '/p' . $in{'pSection'} . '_' . $
+in{'pNum'} . '.html';
[download]

if it still doesn't work you better give us the code where you initialise %in.

Perl is my chainsaw