Just call it and see what happens.

sub bar { print 'woot' }

for my $thing (qw/ foo bar /){
    print "$thing :$/";
    eval{
      no strict refs;
      &{$thing}(@_);  # possibly a nasty symbolic reference
    };
    warn "You can not call $thing: $@ " if $@;
}
[download]

gives you something like:

foo :
You can not call foo: Undefined subroutine &main::foo called at call l
+ine 7.
  at call line 9.
bar :
woot
[download]

The main point being, that you can just catch the die from eval and move on.

Why ask if something looks like it will fail, when you can just suck it and see?

if you're involving objects, UNIVERSAL's can may also interest you