package TimeOffset;

sub import {
    my $pkg = shift;
    my $offset = shift || "+0";

    if ($offset !~ /^[+-]/) {
       $offset = $offset - time;
    }

    *CORE::GLOBAL::time = sub { CORE::time() + $offset };

    *CORE::GLOBAL::localtime = sub {
       return @_ ? CORE::localtime(@_)
                 : CORE::localtime(CORE::time() + $offset);
    };

    *CORE::GLOBAL::gmtime = sub {
       return @_ ? CORE::gmtime(@_)
                 : CORE::gmtime(CORE::time() + $offset);
    };
}

1;

##</code><code>##

use TimeOffset '+3600'; # pretend it's 1hr in the future

##</code><code>##

use TimeOffset '-60'; # pretend it's 1min in the past

##</code><code>##

use TimeOffset 12345678; # pretend the program was started
                         # at 12345678 epoch seconds