Yes, of course.

Just for curiousity, i tried the following:

#!/usr/bin/perl -w

while(<>) { print };
seek(STDIN, 0, 0) or die; 
print "-----PASS 2-----\n"; 
while(<>) {print}
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and ran it with:     > ./t.pl < t.pl and it did read the file twice! How come?
(I was expecting an error like 'non-seekable file' or so.)

When doing

 
    >cat t.pl  | perl t.pl
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it died where it should have (i.e. in the seek()).