@ACCTS = ("1234", "5678", "6959");
open(IN,"InFile.txt");
%acct="";
while (defined($line = (<IN>))){
  foreach $x (@ACCTS) {
     if ($line =~/$x/){
       push(@{$acct{$x}},$line);
     }
  }
}

foreach $key (sort keys %acct){
   print "$key,$acct{$key}[0]\n";
}