use Date::Format

DESCRIPTION: This module provides routines to format dates into ASCII strings. They correspond to the C library routines strftime and ctime.

To obtain the date in the format you asked:

perl -e 'use Date::Format;print time2str("%d-%m-%Y\n", time);'
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citromatik

UPDATE:Since the input date is fixed in format (e.g: 16May07) Date::Format can't be used. The solution that gives tirwhan seems correct