#!/usr/bin/perl
use strict;
use warnings;
use reload;

do {
    print "Hit Enter.\n";
    reload::reload("foo");
    foo::bar();
    reload::reload("reload");
} while <STDIN>;

package reload;
use warnings;
use strict;
{
    no warnings;
    sub reload {
        my ($PM) = @_;
        delete $INC{"$PM.pm"};
        eval "require $PM";
    }
}
1;

package foo;
use strict;
use warnings;
sub bar { print "Works\n" }
1;

__DATA__
C:\>perl test.pl
Hit Enter.
Works

Hit Enter.
Subroutine bar redefined at foo.pm line 4, <STDIN> line 1.
Works

Hit Enter.
Subroutine bar redefined at foo.pm line 4, <STDIN> line 2.
Works

Hit Enter.
Subroutine bar redefined at foo.pm line 4, <STDIN> line 3.
Works

Hit Enter.
Subroutine bar redefined at foo.pm line 4, <STDIN> line 4.
Works

Hit Enter.
Subroutine bar redefined at foo.pm line 4, <STDIN> line 5.
Works
^C
C:\>