In Perl, the operators determine the type of their arguments. The numeric operators treat strings as numbers, and things that don't look like a number get treated as zero.

This explains all your four cases.

If you use warnings;, you are warned that "test" isn't numeric, which makes it more obvious what's going on.

The implication that use warnings; was not present to start with is somewhat disturbing. Can one infer that use strict; is also not a habit?

this was in my "test.pl" when ever i need to test a theory or to just see what happens (the latter in this case) i use this and i don't need to use strict and warnings to test theorys

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Any specific reasons PERL does this.

The same reason perl does anything, duh :)

perlnumber, Basic debugging checklist

Larry wills it!