#! perl -sw
use strict;

$| = 1;

sub shuffle {
	my $ref = @_ == 1 ? $_[ 0 ] : \@_;
	my $n = @$ref;
	for( 0 .. $#$ref ) {
		my $p = $_ + rand( $n-- );
		my $t = $ref->[ $p ];
		$ref->[ $p ] = $ref->[ $_ ];
		$ref->[ $_ ] = $t;
	}
	return unless defined wantarray;
	return wantarray ? @{ $ref } : $ref;
}

warn 'Start   : '.localtime() .$/;
my @data = <>;

warn 'Read    : '.localtime() .$/;

shuffle \@data;

warn 'Shuffled: '.localtime().$/;

print for @data;

warn 'Written : '.localtime().$/;
__END__
P:\test>shuffleFile.pl  data\1millionlines.dat >nul
Start   : Fri Apr 15 19:41:44 2005
Read    : Fri Apr 15 19:41:53 2005
Shuffled: Fri Apr 15 19:41:55 2005
Written : Fri Apr 15 19:41:57 2005