use strict;
use warnings;
use Test::More;
use Test::More::UTF8; # loads utf8.pm

sub convert_currency {
    my %map = (
        '$¥' => sub { $_[0] * 105.4 },
        '¥$' => sub { $_[0] * 0.0095 },
        '$€' => sub { $_[0] * 0.89 },
        '€$' => sub { $_[0] * 1.12 },
    );

    my ($from, $to, $amount) = @_;

    my $converter = $map{"$from$to"};

    return sprintf( '%.3f', $converter->($amount) );
}

is( convert_currency('$', '¥', 5),     '527.000', '$ -> ¥' );
is( convert_currency('€', '$', 42.02),  '47.062', '€ -> $' );
is( convert_currency('$', '€', 42.02),  '37.398', '$ -> €' );

done_testing;