There is module on CPAN that will let you work with dates in the format that you want. Date::Manip. The following code works out the current month and then whether today is the last sunday. Hope you find it useful. 
#!/usr/bin/perl -w

use strict;

use Date::Manip;

my $curmonth = &UnixDate("today","%b");

my $date1=&ParseDate("today");
my $date2=&ParseDate("last sunday in $curmonth");
my $flag=&Date_Cmp($date1,$date2);
if ($flag<0) {
           # date1 is earlier
} elsif ($flag==0) {
           # the two dates are identical
} else {
           # date2 is earlier
}

[download]

Nuance

Baldrick, you wouldn't see a subtle plan if it painted itself purple and danced naked on top of a harpsichord, singing "Subtle plans are here again!"

In reply to RE: Determining when the last day a script will run... by nuance
in thread Determining when the last day a script will run... by Lord Rau

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.