#!/usr/bin/perl

use strict;
use warnings;

{   my %mons = qw( Jan 1 Feb 2 Mar 3 Apr 4 May 5 Jun 6 Jul 7 Aug 8 Sep 9 Oct 10 Nov 11 Dec 12 );
    my $mon_str = join '|', keys %mons;
    my $mon_re = qr/$mon_str/;

    sub fix_bcp_file {
        my ( $file ) = @_;
        local ( $^I, @ARGV ) = ( '.bak', $file );
        while ( <> ) {
            s/(^|\,)($mon_re)\s{1,2}(\d{1,2})\s(\d{4})\s\s?(\d\d?):(\d\d):(\d\d):(\d{3})([AP])M(\,|$)/
              $1 .
              sprintf( '%02d %02d %04d %02d:%02d%sM',
                $mons{ $2 },
                $3,
                $4,
                $5,
                $6,
                $9 ) .
             $10
            /eg;
            print;  # UPDATED thanks runrig
        }
    }
}
for my $file (@ARGV) {
   fix_bcp_file($file);
}