Anonymous Monk has it right, Date::Manip does not recognize the date format (see VALID DATE FORMATS). You will need to parse/correct it yourself:

#!/usr/bin/perl
use strict;
use Date::Manip;

Date_Init("TZ=EST5EDT");

print "Hello, World...\n";

my $date = '30-04-2010';
die "Can't parse date" unless $date =~ s/(\d\d)\-(\d\d)\-(\d\d\d\d)/$3
+-$2-$1/;
$date = UnixDate($date, "%e/%b/%y");

print $date;
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