#!/usr/bin/perl -w
package main;
use strict;

my %dep;
while (<DATA>) {
	my @tasks = split '\s+', $_;
	my $key = shift @tasks;
	$dep{$key} = [@tasks];
}

## check for circular dependencies.
foreach my $k (keys %dep) {
	foreach my $item (@{$dep{$k}}) {
		## is $k in the list for $dep{$item}?
		my $circ = 0;
		foreach (@{$dep{$item}}) { $circ++ if  $_ eq $k }
		die "Circular reference on $k => $item" if $circ;
	}
}

## sort tasks by least number of deps (exec 0-dep tasks first)
my @ord_tasks = sort { scalar(@{$dep{$a}}) <=> scalar(@{$dep{$b}}) } keys %dep;

## "execute" each task, forking for dependencies.
my %exec_hist;
foreach my $task (@ord_tasks) {
	exec_task($task, \%exec_hist, \%dep)
}

sub exec_task {
	my $task = shift;
	my $history = shift;
	my $dep_hash = shift;
	my $level = shift;
	
	my %dep = %$dep_hash;
	defined $level or $level = 0;
	
	return if exists $history->{$task};
	$history->{$task} = undef;
	print "Analyze $task:\n";
	foreach ( @{$dep{$task}} ) {
		#~ print "\n";
		next if exists $history->{$_};
		print ">" for 0..$level;
		exec_task($_, $history, $dep_hash, $level+1);
	}
	print "." for 0..$level-1;
	print "EXEC($task)\n"
}

__DATA__
Task1 Task2 Task3
Task2 Task6 Task4
Task3 Task6 Task4
Task5 Task2 Task3 

##</code><code>##

Analyze Task4:
EXEC(Task4)
Analyze Task6:
EXEC(Task6)
Analyze Task5:
>Analyze Task2:
.EXEC(Task2)
>Analyze Task3:
.EXEC(Task3)
EXEC(Task5)
Analyze Task1:
EXEC(Task1)