#! /usr/bin/perl -w

use strict;

my %replace = ( qw/
    COM  SEC
    MOB  HIS
    MOC  COM
    ICM1 INO
    ICM2 INO
    EU   HIS
    CY   GRE
    AE   MOB
    IN   ICC
    GR   GRE
    MH   MOC
    CO   MOC
    MO   HIS
/);

my @order;
demangle( \%replace, \@order );

sub demangle {
    my $r     = shift;
    my $order = shift;

    my %invert;
    @invert{ values %$r } = keys %$r;

    my( %okay, %collide );

    for my $key( sort keys %$r ) {
        if( exists $invert{$key} ) {
            $collide{$key} = $r->{$key};
        }
        else {
            $okay{$key} = $r->{$key};
        }
    }
    unshift @$order, \%okay;

    if( %collide ) {
        my @loop_keys = sort keys %collide;
        my @loop_vals = sort values %collide;
        my $is_loop = 1;
        for( my $n = 0; $n < scalar @loop_keys; ++$n ) {
            if( $loop_keys[$n] ne $loop_vals[$n] ) {
                $is_loop = 0;
                last;
            }
        }
        if( $is_loop ) {
            warn "\t$_\t$collide{$_}\n" for sort keys %collide;
            die "loop in transforms detected, bailing out\n";
        }
        demangle( \%collide, $order );
    }
}

my $pass = 0;
for my $r( @order ) {
    ++$pass;
    print "Pass $pass\n";
    for my $key( keys %$r ) {
        print "\t$key -> $r->{$key}\n";
    }
}
__END__
# produces:
Pass 1
        COM -> SEC
Pass 2
        MOB -> HIS
        MOC -> COM
Pass 3
        ICM1 -> INO
        ICM2 -> INO
        EU -> HIS
        CY -> GRE
        IN -> ICC
        GR -> GRE
        MH -> MOC
        CO -> MOC
        AE -> MOB
        MO -> HIS