Perl regex substitution

Quick question:

What am I doing wrong?  The script doesn't print anything.

#!/usr/bin/perl

use warnings;
use strict;

my %mon = ('Jan' => '01', 'Feb' => '02', 'Mar' => '03', 'Apr' => '04', 'May' => '05', 'Jun' => '06',
           'Jul' => '07', 'Aug' => '08', 'Sep' => '09', 'Oct' => '10', 'Nov' => '11', 'Dec' => '12');

sub MmmDd
{
    my $mmmddyyyy = shift;
    my ($mmm, $dd, $yyyy) = split(/\s+/, $mmmddyyyy);
    my $string =  "$yyyy-$mon{$mmm}-" . sprintf("%02d", $dd);
    return "$string";
}


while(<>)
{
    s/([A-Z][a-z][a-z])\s+(\d{1,2})\s+(\d{4})/MmmDd("$1 $2 $3")/eg;
}

Select allOpen in new window

Sample data:

81      223456789       Jan 2 1999 02:30 am     1222222232224222        123232345
84      111334411       Jan 7 1999      7777 7777 7777  123232345
85      111334444       Jan 2 1999      7777 7777 7777 7777     123232345
86      777777779       Jan 2 1999      7777 7777 6663  111223333
87      111333333       Jan 2 1999      00001111222233334444    111223333
89      111222222       Jan 2 1999      1234333331114123        923457789
90      111444444       Jan 2 1999      111112111121111 923457789
91      111223333       Jan 2 1999      1111222233334444        923457789
92      777777778       Jan 2 1999      777766661234X   222222221
93      111334444       Jan 05 1999 02:30 pm    X7777 7777      222222221
94      777777778       Jan 2 1999      777766661234X   222222221
95      923456789       Jan 3 1999      3131 7777 7777 7777     443232366
99      776677778       Jan 2 1999      1222222232224222        923457789

Select allOpen in new window

There may be  more than one dates.
I tried (?e) (?-e) but that did not work either.