Feeds Tamper plugin to convert an amount to minor units based on currency in another field

If someone has to work with multiple currencies in a single feeds source, the conversion to minor units can't be hardcoded, but must be based on the currency data Drupal Commerce provides.
I have to work with dinamically specified currencies. I will write a feeds tamper plugin that accepts a currency code or symbol and an amount, and uses commerce_currency_amount_to_decimal() to convert it to minor units. The source data will be from separate fields to not to assume any format.
I have a tamper plugin that has to be modified to work as described above.

The idea is based on issue #1159426: Price is not importing correctly. It imports $1.50 instead of $150 when 150 or 150.00 is the source, especially the work of spiffl and advices by pcambra.