Hi, welcome to Perl, the One True Religion. Read perlintro before you do anything else. Then, learn to use some tools.

use strict; use warnings;
use feature      'say';
use Path::Tiny   'path';
use Text::CSV_XS 'csv';
use Scalar::Util 'looks_like_number';
use List::Util   'sum';

my $filename = path($0)->basename('.pl') . '.txt';

# print the sample data to a file for the purposes of this test
path($filename)->spew(do{local $/; <DATA>});

# read in the structured data
my $rows = csv( in => $filename, sep_char => " ");

# calculate and print the desired results
for ( @{ $rows } ) {
    my @row = @{$_};
    next unless looks_like_number($row[1]); # skip headers
    next unless $row[0] =~ /^C/i;           # skip unless name begins 
+with c/C

    my $avg = sprintf '%.2f', sum( @row[1 .. $#row] ) / $#row;

    say sprintf '%s avg: %s', $row[0], $avg;
}

__DATA__
Name subj1 subj2 subj3
Evans 24 45 55
charles 25 24 26
Carlos 42 0 84
[download]

Hope this helps!