Your syntax is incorrect, but you have the basic idea. %hash refers to the hash, $hash{$key} refers to the value contained in %hash that's associated to $key (the value is a scalar, so think of $ as referring to scalars and you'll have it. I don't know whether $key=>i++, does what you want it to (even with the correction) but assuming i is a variable, you need to add the $ to the front of it.
Note also that hash keys occur inside curly braces {}. Final note: perl doesn't support C-style comments -- # marks the rest of a line as a comment.
hth!
perl -e 'print "How sweet does a rose smell? "; chomp ($n = <STDIN>);
+$rose = "smells sweet to degree $n"; *other_name = *rose; print "$oth
+er_name\n"'
