my ($value, $from, $to, $prefix, %allprefixes);
%allprefixes = 
(
	"mega"	=> 6,  #use these as exponents, so down below I can just subtract exponents to get the answer
	"kilo"	=> 3,
	"milli"	=> -3,
	"micro"	=> -6,
	"nano"	=> -9,
	"pico"	=> -12,
	"femto"	=> -15,
	"atto"	=> -18,
	"zepto"	=> -21,
	"yocto"	=> -24,
);

print "Enter the unit that you are starting with: ";
$from = <STDIN>;
print "Enter your target unit: ";
$to = <STDIN>; 
print "Enter the numerical amount: ";
$value = <STDIN>; 

chomp ($from);
chomp ($to);
chomp ($value);

if (not exists $allprefixes{$to}) {
	die "My programmer has not yet supplied me with $to as a prefix\n";
}
if (not exists $allprefixes{$from}) {
	die "My programmer has not yet supplied me with $from as a prefix\n";
}

$prefix = $allprefixes{$to} -- $allprefixes{$from};

print "$value $from is ",$value*$prefix," $to. \n";