2.5 Simple Hash

%h = (
     London => 19100,
     Amsterdam => 2001,
     Munchen   => 2002,
     Paris     => 2003,
   );

print STDERR "%h\n";

%h

print STDERR "Debug: ", join "|", %h, "\n";

Debug: Paris|2003|London|19100|Munchen|2002|Amsterdam|2001|

print STDERR "Debug: "; 
print STDERR "$_=>$h{$_}|" foreach keys %h;
print STDERR "\n";

Debug: Paris=>2003|London=>19100|Munchen=>2002|Amsterdam=>2001|