while (my $line = <FILE>) {
    $content .= substitute_parameters($line);
}

while (($content) = $sth->fetchrow_array()) {
    $content = substitute_parameters($content);
}

sub substitute_parameters
{
   my ($content) = @_;
   $content =~ s/{{([a-zA-Z0-9\{\'\}_]+)}}/$hash{$1}/ge;
   return $content;
}