Try this... 
#!/usr/bin/perl -w
use strict;

my %x = ( 1 => [qw(d e f)],
      2 => [qw(a b c)],
      3 => [qw(g h i)]
      );

my %rev = map { my $key=$_; map { $_=>$key} @{$x{$key}} } keys %x;
print "$_ -> $rev{$_}\n" foreach sort keys %rev;

[download]

The trick (imho) is to build the "reverse" hash first and then deal with sorting / outputing that after the fact.

Btw, I'd suggest not using non-standard notation, even if it's comfortable for you. It'll (potentially) make things harder when you're trying to show other people.

In reply to Re: Reorganising a Hash for Output by bmcatt
in thread Reorganising a Hash for Output by arunhorne

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