use warnings;
use strict;
use Data::Dump qw(dd pp);

my %hash =
(
    a => 11,
    b => 12,
    c => 13,
    d => 14,
);

while (my ($key, $value) = each %hash)
{
    print "key is $key, value is $value, hash is ", pp(\%hash), "\n";
    delete $hash{$_} for qw( a b c d );
    $hash{x} .= $key;
}

dd \%hash;

##</code><code>##

23:43 >perl 1148_SoPW.pl
key is c, value is 13, hash is { a => 11, b => 12, c => 13, d => 14 }
key is x, value is c, hash is { x => "c" }
key is x, value is cx, hash is { x => "cx" }
key is x, value is cxx, hash is { x => "cxx" }
key is x, value is cxxx, hash is { x => "cxxx" }
key is x, value is cxxxx, hash is { x => "cxxxx" }
key is x, value is cxxxxx, hash is { x => "cxxxxx" }
key is x, value is cxxxxxx, hash is { x => "cxxxxxx" }
key is x, value is cxxxxxxx, hash is { x => "cxxxxxxx" }
key is x, value is cxxxxxxxx, hash is { x => "cxxxxxxxx" }
...