#!/usr/bin/perl

use strict;
use warnings;

use Date::Manip;

my $date_manip_object = new Date::Manip;

$date_manip_object->parse( '2 days ago' );
$date_manip_object->convert( 'GMT' );

my $gmt_ref = $date_manip_object->printf( '%Y%m%d') ;

while (<DATA>) {
    my $err = $date_manip_object->parse_format('.*?\\[%d/%b/%Y:%T\s+%z
+\\].*', $_);

    next if $err; # skip (?) lines that do not match the date format

    my $input_line_date = $date_manip_object->printf( '%Y%m%d') ;

    if ($input_line_date eq $gmt_ref) {
       print;
    }
}

__DATA__
10.1.10.178  -       -       [15/Jun/2010:23:30:34    +0000]      -
10.1.10.178  -       -       [16/Jun/2010:23:30:34    +0000]      -
[download]

my $date_manip_object = new Date::Manip;
[download]

Where in the documentation did you find that usage? It doesn't work because the module does not work that way. Read Date::Manip.

10.1.10.178  -       -       [15/Jun/2010:23:30:34    +0000]      -
10.1.10.178  -       -       [16/Jun/2010:23:30:34    +0000]      -
[download]

The date and time is in GMT. I should convert to PST time.

#!/usr/bin/perl


use Date::Manip;

$date = ParseDate("2 days ago");
print $date
[download]

This works and why created a object doenst work.