Put the following in a file,

defined(my $v = <>) or exit;
my ($c,@c) = 1;
open($_, "|-", "$^X $0") for @c[0,1];
$_ eq $v ? ++$c : print { $c[ $_ lt $v ] } $_ while <>;
pop @c;
print $v x $c;
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, and run it with an unsorted text file either on stdin, or as a command line argument. The output will be sorted.