#!/usr/bin/perl -w
#
print "Please put in the username for which you want to setup a virtual host:\n";

my $user = <STDIN>;
my @fields = ();
my $fields = ();

open TPL, "vh_template.tpl";
my @vhost = <TPL>;
close TPL;

foreach my $vhost(@vhost){
        if ($vhost =~ /^ServerName/){
                @fields = split /\./, $vhost;
                $fields = @fields;
                s/$fields\[0\]/$user/; #this line generates the error
                print "$fields[0]\n";
                }
}