When you use my $hostmatch inside the if, you're creating a variable that only exists within the if. Any value you assign to it will disappear along with the variable once outside the if. That means elsif( $hostmatch == 1 ) is using a variable that no longer exists. The solution is:

my $hostmatch;
while( $row = $sth->fetchrow_hashref ) {
    if( $host eq $row->{host} ) {
        $hostmatch = 1;
    }
}
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Same goes for $data. Change

if( param('select') and param('select') !~ /\.\./ )
{
    my $data = ...
    ...
}
[download]

to

my $data;
if( param('select') and param('select') !~ /\.\./ )
{
    $data = ...
    ...
}
[download]