Fast alternative to grep -f

Question

file.contain.query.txt

ENST001

ENST002

ENST003

file.to.search.in.txt

ENST001  90

ENST002  80

ENST004  50

Answer 1

use strict;
use warings;

system("sort file.contain.query.txt > qsorted.txt");
system("sort file.to.search.in.txt  > dsorted.txt");

open (QFILE, ") {
  my ($queryid) = ($qline =~ /ENST(\d+)/); 
  while (my $dline = ) {
    my ($dataid) = ($dline =~ /ENST(\d+)/);
    if ($dataid == $queryid)   { print $qline; }
    elsif ($dataid > $queryid) { break; } 
  }
}