If you want to stay with Date::Manip, you'll have to feed the parser with a valid date: 'NOV-07' is not a date, but a month (there is no day specified).

Taking care of that, the following code works:

#!/usr/bin/perl

use strict;
use warnings;

use Date::Manip;

my $thingy = 'NOV-2007';
my $date = UnixDate( ParseDate( "1-$thingy" ), '%Y/%m' );

print "$date\n";
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Good luck,