and your question is what?

As an aside the code you give doesn't do what you seem to want. The following may suit you better:

#!/usr/bin/perl
use warnings;
use strict;

my $groupCode;
my @members;

while (defined(my $line = <DATA>) || $groupCode) {
    if (defined($line) && $line !~ /^(\d+)$/) {
        chomp $line;
        push @members, $line if defined $groupCode;
        next;
    }

    if (defined $groupCode) {
        @members = '-- no members --' if !@members;
        print "$groupCode ", join(', ', @members), "\n";
    }

    $groupCode = $1;
    @members   = ();
}


__DATA__
50000
Craig
Mark
50001
Craig
Steve
50002
Durlene
Floyd
Jeremy
Kent
Leroy
Jessie
Rocky
Sean
Craig
Jeffrey
Rick
[download]

Prints:

50000 Craig, Mark
50001 Craig, Steve
50002 Durlene, Floyd, Jeremy, Kent, Leroy, Jessie, Rocky, Sean, Craig,
+ Jeffrey, Rick
[download]