In perldata, you can see : If you evaluate an array in scalar context, it returns the length of the array. (Note that this is not true of lists, which return the last value....

Your sub bad() returns the value of the last expression evaluated (see return). The last and unique expression in bad() is a list :

• list in scalar context -- each element of this list is evaluated and the last one is returned
• list in list context -- bad() returns the list (3 elements) then scalar counts the number of elements. List context can be forced with  () = ... (see examples).

use strict;

sub good { my @a = qw/zero one two/; @a }
sub bad  { qw/foo bar baz/ }

print scalar good(), "\t<== what I want";
print "\n";
print scalar bad(),  "\t<== not";
print "\n";
print scalar ( () = bad()),  "\t<== list context, then scalar()";
print "\n";
print "baz is ".bad();
print "\n";
print "1+2 = ".(  () = bad());
print "\n";
__END__

Output:
3    <== what I want
baz    <== not
3    <== list context, then scalar()
baz is baz
1+2 = 3
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