use strict;

@filelist = ("f1");

while(<DATA>){
  chomp;
  /^([^\t]*)\t/; # I assume it is tab seperated
  my $rec = $1;
  foreach my $file(@filelist){
    my $entry = qx(grep -P "^$rec\t" $file);# I assume it is tab seperated
    print "$rec\t$file\t$entry";
  }
}


__DATA__
K	1
J	2
L	3
H	4


##</code><code>##

open (OUT, ">", $myoutfile) || die "$!"