For future reference (as you already have the answer from roboticus), here's a basic debugging technique which can open your eyes to the effects that unexpected data can have on your code: Display what you have, not what you think you have.

Example: Your approach to displaying the information:

    print "Preforming sha1 on $file";
    system( "sha1sum $file > data" );
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Produces:

    Preforming sha1 on test1.dat
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This is fine for human user display, but for programmer debugging display, you've left yourself open to a number of "dirty screen tricks". Instead:

    my $systemCommand = "sha1sum $file > data";
    print "\$systemCommand = [$systemCommand]\n";
    system( $systemCommand );
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Produces:

    $systemCommand = [sha1sum test.dat
     > data]
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Notice how the newline jumps out at you when displayed this way.

I would be remiss to not note that there are two modules folks love to use which might also reveal these problems and more -- Data::Dumpand Data::Dumper. I've seen the effectiveness at these modules helping Monks zero in on a user's issues as if they were painted with red Xs. I highly recommend their use whenever you want to peek at your data in more depth.