To sort by ascending value:

say "$_: $coins{$_}" for sort { $coins{$a} <=> $coins{$b} } keys %coins;

To sort by descending value:

say "$_: $coins{$_}" for sort { $coins{$b} <=> $coins{$a} } keys %coins;

To sort by ascending value followed by descending key (not really applicable for this coin example, but good to know):

say "$_: $coins{$_}" for sort { ( $coins{$a} <=> $coins{$b} ) || ( $a cmp $b ) } keys %coins;

Note: Be sure to use <=> for numerical sorts and cmp for alphabetical.