use strict;
use warnings;

my %locations = ( USA => { NY => '212',
                           NJ => '973' },
                  ENG => { LDN => '44',
                           CVT => '20' } );

foreach (keys %locations) {
  process_article(\%{$locations{$_}});
}

sub process_article
{
  my $hash = shift @_;
  print "$_ $hash->{$_}\n" foreach (keys %$hash);
}