use B::Deparse;
my $d = B::Deparse->new;
# anonymous sub
my $coderef = sub { print "howdy!" }; # assuming herveus ;)
my $code = $d->coderef2text($coderef);
# named sub, e.g. coderef2text from B::Deparse
$code = $d->coderef2text(\&B::Deparse::coderef2text);