Thanks everyone for your help, but I think I've got a solution - and it's even simpler than I hoped for. Take a look at this:

sub there {
  print "I'm here!";
}

my %refs = (there => \&there,
            not => \&not_there,
            anon => sub { "I'm here too!" });

foreach (keys %refs) {
  print "'$_' is ", defined &{$refs{$_}} ? "valid\n" : "invalid\n";
}
[download]

Which displays:

'there' is valid
'not' is invalid
'anon' is valid
[download]

Much kudos to Matt Freake of London.pm for coming up with the solution - defined &$coderef.

--
<http://www.dave.org.uk>

European Perl Conference - Sept 22/24 2000, ICA, London
<http://www.yapc.org/Europe/>