# config:
my $field = 0;
my $sep = "\t";




$, = $sep;
$\ = $/;

my %file; # { num, name, $fh }

my $fnum = 1;

while (<>)
{
	chomp;
	my @c = split /$sep/o;

	my( $key, $num ) = defined $c[$field]
		? ( $c[$field], $fnum++ )
		: ( '(column not present)', 0 );

	unless ( $file{$key} )
	{
		$file{$key}{num} = $num;
		$file{$key}{name} = sprintf 'part.%03d', $file{$key}{num};
		-f $file{$key}{name} and die
			"Sorry, '$file{$key}{name}' exists; won't clobber."; 
		open $file{$key}{fh}, ">", $file{$key}{name} or die
			"Error opening '$file{$key}{name}' for write - $!";
	}

	print {$file{$key}{fh}} @c;
}

print $file{$_}{name}, $_
	for sort { $file{$a}{num} <=> $file{$b}{num} } keys %file;