One hack you could try:

Define a AUTOLOAD-sub and then call the code-ref that does not exist.

The call will then end up in the AUTOLOAD-sub where the (fully qualified) name of the sub is then available in the $AUTOLOAD-variable.

e.g.:

use strict;
use warnings;
use vars qw($AUTOLOAD);

my @q = (\&abc, \&def);
my $msg;
my $param = "hhhhhh";

foreach my $q (@q) {
    if (defined(&$q)) {
        $msg .= $q->($param);
    } else {
        my $name = $q->();
        $msg .= "cannot call $name\n";
    }
}
print $msg;


sub abc {
    my $q = shift;
    return "hello from ABC($q)\n";
}

sub AUTOLOAD {
  return $AUTOLOAD;
}
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This will produce "cannot call main::def".

Getting rid of the package-part is an easy exercise left for the reader.