Simply copy this code into the top of your Perl script and enjoy. All print statements will go straight to users browser and render instantly.

$|++;
print "Content-type: text/html\r\n";
print "Content-Encoding: plain\r\n\r\n";
&load_buffer; 
sub load_buffer {
        my $cmd = qq{perl -e "\$|++; print ' ' and sleep(1) for 1..1"};
        open my $PROC, '-|', $cmd or die $!;
        while (sysread $PROC, $buffer, 1) { print " ", ' ' x 1000, "\n";}
}

The explanation

$|++; #This is needed to disable buffering
print “Content-type: text/html\r\n”;
# This header is a quick hack to deny browser to gzip/deflate your output
print “Content-Encoding: plain\r\n\r\n”;
&load_buffer; #keeps the browser window printing progress while script runs

sub load_buffer {
my $cmd = qq{perl -e “\$|++; print ‘ ‘ and sleep(1) for 1..1”};
open my $PROC, ‘-|’, $cmd or die $!;
while (sysread $PROC, $buffer, 1) { print ” “, ‘ ‘ x 1000, “\n”;}

}