with select

use autodie;
{
    open my($out), '>', 'out.xml';
    my $saver = select $out;
    my $parser = HTML::Parser....
    print ... # all output goes into $out;
    
    select $saver;
}
print "all output goes back into STDOUT";
[download]

or with SelectSaver

use autodie;
use SelectSaver;
{
    open my($out), '>', 'out.xml';
    my $saver = SelectSaver->new($out);
    my $parser = HTML::Parser....
    print ... # all output goes into $out;
    
}
print "all output goes back into STDOUT";
[download]