===================================
#!/usr/bin/perl -w

use strict;

print "Begin...\n";
for ( my $i = 0; $i < 5; $i++ )
{
        print "$i...\n";
        sleep 2;
}
===================================

##</code><code>##

$ ./populate.pl > data.txt&

##</code><code>##

$ tail -f data.txt

##</code><code>##

while [ 1 ]; do echo "some text..."; done > data.txt&