I would read each record complete rather than one line at a time, and to keep it simple, would push scores into an anonymous array per student. Then just iterate over each student and do the math.

use List::Util qw( sum );

my %student;

local $/ = '';

while( <DATA> ) {
  push @{$student{$1}}, $2 and next if m/\A([^\n]+).+?(\d+)\n?\Z/s;
  warn "Invalid record #$.: <<$_>>\n";
}

while( my( $name, $scores ) = each %student ) {
  print "$name: Average ", sum( @{$scores} ) / @$scores, "\n";
}

__DATA__
Jack
Student ID - 12445
Math Score - 45

Jill
Student ID - 234254
Math Score - 90

Jack
Student ID -12445
Math Score2 - 33

Jill 
Student ID - 234254
Math Score2 - 10

[download]

Dave

In reply to Re: Selecting successive lines by davido
in thread Selecting successive lines by zee3b

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.