Awright.... ;-)

Just hadda' check, following my own suggestion above. Installed requisite modules, tweaked code and came up with this:

#!/usr/local/bin/perl
use 5.016; use warnings; 
# 1071094
use utf8;
use Locale::Currency;
use File::Basename;
use Cache::FileCache;
use Finance::Quote;
use POSIX;

say "FOO: ". get_price("CHF","EUR","50") . "\n";

sub get_price {

my ($currency_from,$currency_to,$amount) = @_;

my ($filename) = fileparse($0, '.pl');

my $cache = Cache::FileCache->new({
    cache_root         => "$ENV{HOME}/.$filename",
    default_expires_in => '1 day',
});

my $quote = Finance::Quote->new();

my $ratio = $cache->get("$currency_from:$currency_to");
say "\$ratio: $ratio \t \$currency_from $currency_from \t \$currency_t
+o: $currency_to";
$ratio = $quote->currency($currency_from, $currency_to)
    unless defined $ratio;
say "\$ratio: $ratio, \t \$currency_from $currency_from, \t \$currency
+_to: $currency_to";
die "sorry, cannot convert from $currency_from to $currency_to\n"
    unless defined $ratio;

$cache->set("$currency_from:$currency_to", $ratio);

return $amount * $ratio
}
[download]

Execution:

C:\> 1071094.pl
Use of uninitialized value $ENV{"HOME"} in concatenation (.) or string
+ at D:\_Perl_\PMonks\1071094.pl line 19.
$ratio: 0.8113   $currency_from CHF      $currency_to: EUR
$ratio: 0.8113,          $currency_from CHF,     $currency_to: EUR
FOO: 40.565
[download]

The 'uninitialized' isn't exactly surprising; nor does it appear to be crucial. The rest is plausible, but of undetermined correct-ness.