#!/usr/bin/perl
my $s = sub { my $k = shift; return $k;};
use B::Utils qw( walkoptree_simple );
print walkoptree_simple( $s, { print } );
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Looks like this does the job:

my $s = sub { my $k = shift; return $k;};
use B::Deparse;
my $deparse = B::Deparse->new("-p", "-sC");
print  $deparse->coderef2text($s);
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The morale here: when in doubt, ask, but don't wait for the answer, work on it...

That of course "does the job" for a limited subset of coderefs, since at the moment there's no way to know the closure bindings (or get at them for their current values), so it'll come back to life pointing at an entirely wrong set of closure-bound variables.

This is a known issue, and being considered during the development of the Perl6 runtime engine.

-- Randal L. Schwartz, Perl hacker