For example, you can say

    use Interpolation 
        money     => \&commify_with_dollar_sign,
        E         => 'eval',
        placename => 'ucwords';

And then you can write these:

    print "3 + 4 = $E{3+4}";
    # Prints  ``3 + 4 = 7''

    $SALARY = 57500;
    print "The salary is $money{$SALARY}";
    # Prints  ``The salary is $57,500.00''