tempfile.txt is size 35 Mb
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x177fa280250 " Querysome random text 0.271320203145251\n"\0
  CUR = 41
  LEN = 408
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x177fa34f4d0 " Querysome random text 0.775348369818055some random text 0.775348369818055\n"\0
  CUR = 75
  LEN = 201
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x177fa3a28b0 " Querysome random text 0.785001144808529\n"\0
  CUR = 41
  LEN = 43
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x177fa297c60 " Querysome random text 0.894431999356865\n"\0
  CUR = 41
  LEN = 309
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x177f88a13b0 " Querysome random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259\n"\0
  CUR = 313
  LEN = 392
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x177fa3750d0 " Querysome random text 0.809515115277865\n"\0
  CUR = 41
  LEN = 275
  COW_REFCNT = 2
0.005142 read lines from disk and do RE (6 matches).


SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x177f88b3ed0 " Querysome random text 0.271320203145251\n"\0
  CUR = 41
  LEN = 656
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x1778000b070 " Querysome random text 0.775348369818055some random text 0.775348369818055\n"\0
  CUR = 75
  LEN = 37784908
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x1778242b070 " Querysome random text 0.785001144808529\n"\0
  CUR = 41
  LEN = 37784634
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x1778000d070 " Querysome random text 0.894431999356865\n"\0
  CUR = 41
  LEN = 37784593
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x1778242b070 " Querysome random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259some random text 0.412049736815259\n"\0
  CUR = 313
  LEN = 37784176
  COW_REFCNT = 2
SV = PV(0x177f89db120) at 0x177f88bcca0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x1778000f070 " Querysome random text 0.809515115277865\n"\0
  CUR = 41
  LEN = 37783182
  COW_REFCNT = 2
0.004073 read lines from in-memory file and do RE (6 matches).


##</code><code>##

#!/usr/bin/env perl

use warnings;
use strict;
use Time::HiRes qw( time );
use Devel::Peek;


my $file = shift @ARGV;
my ($fh, $time);

if (!$file) {
    #  should use Path::Tiny::tempfile
    $file = 'tempfile.txt';
    open my $ofh, '>', $file or die "Cannot open $file for writing, $!";
    
    srand(1234567);
    
    for my $i (0..200000) {
        my $string = 'some random text ' . rand();
        $string = $string x (1 + int (rand() * 10));
        if (rand() < 0.163) {
            $string = " Query${string}";
        }
        say {$ofh} $string;
    }
    $ofh->close or die "Cannot close $file, $!";
    printf "%s is size %i Mb\n", $file, (-s $file) / (1028**2);
}


open $fh, "<", $file;
$time = time;
my $match_count1;
my $i1 = 0;
while(<$fh>) {
  /^ ?Query/ && $match_count1 ++;
  if (/^ Query/) {
        Dump $_;
        $i1 ++;
        last if $i1 > 5;
  }
}
printf "%f read lines from disk and do RE ($match_count1 matches).\n", time - $time;

seek $fh, 0, 0;
my $s = "";
while(<$fh>) {
  $s .= $_;
}
$fh->close;


#Dump $s;

print "\n\n";

open $fh, "<", \$s;
$time = time;
my $match_count2;

my $i2 = 0;
while(<$fh>) {
  /^ ?Query/ && $match_count2++;
  if (/^ Query/) {
    Dump $_;
    $i2++;
    last if $i2 > 5;
  }

}
printf "%f read lines from in-memory file and do RE ($match_count2 matches).\n", time - $time;