use strict;
use warnings;

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

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


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