c:\test>type junk.pl
print while <>;

c:\test>perl junk.pl junk.pl
print while <>;

c:\test>perl junk.pl < junk.pl
print while <>;

c:\test>junk.pl junk.pl
print while <>;

c:\test>junk.pl < junk.pl
print while <>;

c:\test>junk junk.pl
print while <>;

c:\test>junk < junk.pl
print while <>;

c:\test>del junk.pl

c:\test>copy con junk.pl
print "'$_'" while <>;
^Z
        1 file(s) copied.

c:\test>type junk.pl | perl junk.pl
'print "'$_'" while <>;
'
c:\test>type junk.pl | junk.pl
'print "'$_'" while <>;
'
c:\test>type junk.pl | junk
'print "'$_'" while <>;
'