foreach my $key (%HASH) {
    $html =~ s/<!--$key-->/$HASH{$key}/gis;
}#foreach
print $html;

##</code><code>##

foreach my $key (%HASH) {

##</code><code>##

foreach my $key (keys %HASH) {

##</code><code>##

my $userinput = 'Some text';
$html =~ s/<!--usertext-->/$userinput/is;

##</code><code>##

my $userinput = 'Some text :)';
$html =~ s/<!--usertext-->/$userinput/is;