C:\MyDir>perl foo.pl
bar

C:\MyDir>cd ..

C:\>perl foo.pl
Can't open perl script "foo.pl": No such file or directory

C:\>perl -I C:\MyDir foo.pl
Can't open perl script "foo.pl": No such file or directory

C:\>set PATH=%PATH%;C:\MyDir

C:\>perl foo.pl
Can't open perl script "foo.pl": No such file or directory

C:\>perl C:\MyDir\foo.pl
bar