nysus recently asked whether there was a way to get at all the currently open filehandles. Together with Discipulus I concocted a module which does that. It records open, close along with their respective time, and drops filehandles from the track record as soon as they get undefined or go out of scope.

package FileHandle::Track;
use Time::HiRes qw(gettimeofday);

use Hash::Util::FieldHash qw(id_2obj);

my %fd;

BEGIN{
    Hash::Util::FieldHash::fieldhash %fd;
    my $open = sub {
        @_ > 2 ? open $_[0],$_[1],$_[2] : open $_[0], $_[1];
    };
    my $close = sub { close $_[0] };

    *CORE::GLOBAL::open = sub {
        my $result = $open->(@_);
        if ($result) {
            $fd{$_[0]}->{open}     = join " ",@_[1,2],caller;
            $fd{$_[0]}->{opentime} = join ".", gettimeofday;
        }
        $result;
    };
    *CORE::GLOBAL::close = sub {
        my $result = $close->(@_);
        $fd{$_[0]}->{close} = join " ", caller;
        if ($result) {
            $fd{$_[0]}->{close} .= " (closed)";
        } else {
            $fd{$_[0]}->{close} .= " (close failed)";
        }
        $fd{$_[0]}->{closetime} = join ".", gettimeofday;
        $result;
    };
}

sub get_fds {
    return { map { id_2obj($_), $fd{$_} } keys %fd };
}
[download]

After making that into a module proper (tests, documentation with due credits) I'll upload that to cpan.

Any suggestions, critics, enhancements?