You can find the size of the file using the -s file test operator

my $fileSize = -s $fileName;
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or by using the stat() built-in

my $fileSize = (stat $fileName)[7];
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then you can decide how many bytes (always assuming characters are bytes) to read

my $limit = 160;
my $bytesToRead
   = $fileSize > $limit
   ? $limit
   : $fileSize;
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then use read() to read in what is appropriate (being sure to test for a successful read) and print it

my $bytesRead = read($inpFH, my $inpBuffer, $bytesToRead);

die qq{Bad read: read $bytesRead, expected $bytesToRead\n}
   unless $bytesRead == $bytesToRead;

print $inpBuffer;
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I haven't shown getting and validating the file name or the opening and closing of filehandles here.

I hope this is of use.

Cheers,

JohnGG