# condition will not be true but raises no error
if (defined foo) {
    print ref(foo);
};

# raises an error as foo is marked as sub
die "strange .." if foo() eq 'bar';

# also
die "strange .." if (foo() eq 'bar');

# and even this does not show up _any_ errors or warnings
#!/usr/bin/perl -w
use strict;
use diagnostics;
.
.
.
print ref(foo);

# So is foo something special ?
# No, no error or warning also
# when replacing above line simply with
print ref(bar);