#!/usr/bin/perl -w
use strict;

for (qw(foo bar)) {
        ($main::{$_} or sub { print "No such sub: $_\n" })->();
}

sub foo {
        print "Yes, I'm here.\n";
}
__END__
Yes, I'm here.
No such sub: bar

##</code><code>##

(UNIVERSAL::can('main', $sub) or sub { print "No such sub: $_\n" })->();