I've made too many mistakes coverting dates with my own code. I almost always reach for Date::Parse and Date::Format which give you the very handy str2time and time2str subs.

In this case though, NOV-07 was too ambiguous for str2time. Adding 1- to make 1-NOV-07 fixed it.

#!/usr/bin/perl

use warnings;
use strict;

use Date::Format;
use Date::Parse;

my $thingy = q{NOV-07};

my $time = str2time(qq{1-$thingy});
my $date = time2str(q{%Y/%m}, $time);

print  $date;
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2007/11
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