This might work better:

#!/usr/bin/perl

use CGI::Carp qw(fatalsToBrowser);
use CGI;
 my $req = new CGI;
 my $webpage1 = $req->param("first");
 my $filepath = "C:/inetpub/wwwroot/fil.txt";
 my $newtext = "$webpage1\n";


print
     $req->header,
     $req->start_html('Web Pages for local data.');

open (FILE, ">>$filepath") or die "Did not write:$!\n";
print FILE $newtext;
close (FILE);

print
     $req->p('Data Submitted'),
     $req->br($req->b('$webpage1')),
     $req->end_html;
[download]