#!/usr/bin/perl -w
use strict;

# Emulate:
#  $ date -d "Tue, 01 Jan 2013 16:05:53 +0000"
# Tue Jan  1 10:05:53 CST 2013

use Time::Local qw< timegm >;
use POSIX       qw< strftime >;

my @Mons = qw< jan feb mar apr may jun jul aug sep oct nov dec >;
my %Mons;  @Mons{@Mons} = 1..@Mons;

print datetime_offset2local( "@ARGV" ), $/;
exit;

sub datetime_offset2local {
    my( $date ) = @_;

    # Parse out the date parts:
    my( $dow, $day, $mon, $yr, $time, $off, $ex ) = split /,? /, $date, -1;
    die "Too many fields ($ex) in input datetime ($date)\n"
        if  defined $ex;
    my( $hr, $min, $sec ) = split /:/, $time;
    $mon = $Mons{ lc $mon }
        ||  die "Invalid month name ($mon): $date\n";

    # Convert input date to epoch seconds (ignoring GMT offset):
    $sec = timegm( $sec, $min, $hr, $day, $mon-1, $yr );

    # Parse the GMT offset and apply it:
    ( my $sign, $hr, $min ) = $off =~ /^([-+])([0-9][0-9])([0-9]*)$/
        or  die "Invalid offset ($off): $date\n";
    $off = $hr*60;
    $off += $min || 0;
    $off *= 60;
    $off *= -1
        if  '-' eq $sign;

    # Convert epoch seconds to string using local time zone and locale:
    return strftime( "%a, %b %d %Y %T %Z (%z)", localtime( $sec - $off ) );
}

__END__

 $ TZ=US/Central perl offset2local.pl Tue, 01 Jan 2013 16:05:53 +0000
Tue, Jan 01 2013 10:05:53 CST (-0600)

 $ TZ=US/Central perl offset2local.pl Tue, 01 Jan 2013 16:05:53 -0600
Tue, Jan 01 2013 16:05:53 CST (-0600)

 $ perl offset2local.pl Tue, 01 Jan 2013 16:05:53 +0000
Tue, Jan 01 2013 08:05:53 PST (-0800)