$ echo 'package Tom;' > foo.pl

$ chmod u+x foo.pl

$ ./foo.pl              
package: not found

##</code><code>##

$ ./foo.pl 2>&1 | splain
package: not found (#1)
    (A) You've accidentally run your script through the
    Bourne shell instead of Perl.  Check the #! line, or
    manually feed your script into Perl yourself.