#!/usr/bin/perl -l

# http://perlmonks.org/?node_id=1170935

use strict;
use warnings;

sub flip { join '', reverse map tr/-+/+-/r, /\w./g }

my $all = ' ' . join ' ', map { "$_," . flip() . ' ' } map tr/ :\n//dr
+, <DATA>;

my %firsts;
@firsts{ $all =~ /[, ](\w[+-])/g } = ();
my @queue = map "$_ $all", sort keys %firsts;

while( $_ = shift @queue )
  {
  if( /^(\S+)\s*$/ )
    {
    print join ' : ', $1 =~ /\w./g;
    }
  else
    {
    /^(\S*)(\w.)( .*? )\2([\w+-]*),[\w+-]*( .*)$(?{
      push @queue, "$1$2$4$3$5" })(*FAIL)/;
    /^(\S*)(\w.)( .*? )[\w+-]*,\2([\w+-]*)( .*)$(?{
      push @queue, "$1$2$4$3$5" })(*FAIL)/;
    }
  }

__DATA__
A+ : B+
C+ : D- : E-
E- : B-

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In reply to Re: Formalizing an array type problem, looking for solution by Anonymous Monk
in thread Formalizing an array type problem, looking for solution by melmoth

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