You need to print the variable $fivefirstfile1, but you're printing the non-defined variable $fivefprot1.
If you're using string and warnings, you can catch it.

You might want to consider using something like this:

use strict;
use warnings;

my $file = $0;
open(my $fh, '<', $0) or die "$file: $!";
my @lines = <$fh>;
my $chars = substr($lines[7], 0, 5);
print "Five first characters are: <$chars>\n";
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