Show us what you have tried and we'll help you sort out the problem areas. It helps us a lot to help you if you provide a small test script we can run without having to mock up your test environment. See I know what I mean. Why don't you? for tips on how to generate any files you might need for the test script.

Note that to test your solution you can probably get away with a couple of short files and only require 2 (instead of 25) "matches among all of them".

This is what I have so far, I know it is a mess. I'm not quite sure if this was the best way to incorporate the test files, but I put them at the bottom under DATA.

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


my @files = shift
foreach my $file (@files) {
    open my $fh, '<', $file
        or die "Couldn't read '$file': $!";
    
    while (<$fh>) {
        my %names;
        my $name ;
        my $number;   
        
          $name = $1;
          $name = split(',', $files);
    };



__DATA1___
A12345,23
A22334,100
A22789,44
A10923,89

__DATA2___
A89224,88
A12345,99
A78663,100
A10923,89

Expected output: given 2 matches present and at least one in each file
A10923
A12345
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Somebody's in the same class as this guy. Or at least, the problems are remarkably similar. I suggest you check that thread as well for some ideas. Applefritter's just about written your homework for you.

my (%f_count,%n_count);

for my $file (@files) {
    open( my $fh, '<', $file ) or die "Couldn't read '$file': $!";
    
    while (my $line = <$fh>) {
        chomp $line;
        next unless $line;
        my ($name,$number) = split(',',$line);
        $n_count{$name}++;
        $f_count{$name}{$file}++;
    }
}
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my $num_of_files = scalar @files;
my $min = 25;
my @candidates = grep { $n_count{$_} >= $min } keys %n_count;

for my $name (@candidates) {
    my $in_files = scalar keys %{ $f_count{$name} };
    next unless $in_files == $num_of_files;
    print "$name\n";
}
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