use strict;
use warnings;
use v5.12;

my ( $a, $b, $c, $d );

my %hash = ( 
    'a' => 'apple', 
    'b' => 'banana', 
    'c' => 'cantaloupe', 
    'd' => 'dice', 
);

my $n = 1;
foreach my $symbol ( keys %hash ) {
    say "Iteration ", $n++, ": $symbol => $hash{$symbol}";
    say "\tExecuting as follows: \$$symbol = \$hash{\$symbol}\n";
    eval "\$$symbol = \$hash{\$symbol}"; # <--------- The evil.
}

foreach my $symbol ( qw/a b c d/ ) {
    say "\$$symbol now contains ",
        eval "\$$symbol"; # Once we start the evil it's hard to stop.
}