If the leading zero in your data is significant then that field is a string and not a number and should therefore be stored in a text field[1].

Perl isn't doing anything to the data, it's MySQL that is storing "055555" in a number field and thereby converting it to the smallest equivalent number - 55555.

If you have text, then store it in a text field.

[1] Ignoring the possibility that it's an octal number - in which case you should convert it to decimal before storing in the database.