Why don't I get any syntax errors when I execute my Python script with Perl?

I just wrote some testing python code into test.py, and I'm launching it as follows:

perl test.py

After a while I realized my mistake. I say "after a while", because the Python code gets actually correctly executed, as if in Python interpreter!

Why is my Perl interpreting my Python? test.py looks like this:

#!/usr/bin/python

...Python code here...

Interestingly, if I do the opposite (i.e. call python something.pl) I get a good deal of syntax errors.

From perlrun,

> If the #! line does not contain the word "perl" nor the word "indir" the program named after the #! is executed instead of the Perl interpreter. This is slightly bizarre, but it helps people on machines that don't do #! , because they can tell a program that their SHELL is /usr/bin/perl, and Perl will then dispatch the program to the correct interpreter for them.

For example,

$ cat a
#!/bin/cat
meow

$ perl a
#!/bin/cat
meow