#! perl -slw use strict; use Data::Dumper; sub unwindDependancies{ my ($hashref) = @_; my %copy = %{$hashref}; my @keys = keys %$hashref; my @deps; for (@keys) { next unless exists $copy{$_}; push @deps, [ $_ ]; while( exists $hashref->{$_}) { unshift( @{ $deps[-1] }, $_ = $hashref->{$_} ); @{$deps[-1]} > @keys and die('Circular reference found involving:', "@{$deps[-1]}"); delete $copy{$_}; } } my %h; for (@deps) { my $r = \%h; $r = exists $r->{$_} ? $r->{$_} : ($r->{$_} = {}) for @$_; } #print Dumper \%h; my (@order, @stack); my $r=\%h; my $t=0; { while(my ($key, $val) = each %$r) { push @order, $key; push(@stack, $r), $r = $val, next if keys %$val; } $r = pop(@stack), redo if @stack; } # print "@order"; return @order; } my %test = ( qw[A B B C D E E F F G G C J H H F I H K H N M O P P Q Q N S U T V]); print join' ', unwindDependancies \%test; 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 / ); print join' ', unwindDependancies \%replace; __DATA__ C:\test>238721 V T C G F H I J K E D B A U S M N Q P O ICC IN SEC COM MOC CO MH HIS EU MO MOB AE GRE CY GR INO ICM1 ICM2