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

timethese(100000 => {
 normal         => sub {
 open my $in, "< molpro.out" or die "geht nicht\n";
 my ($r1,$r2,$r3) = (1,1,0);

 while (<$in>){
  if (($r1) && (/^\s*?!MCSCF STATE (\d+).1 ENERGY/)){my $x = $1}
  if (($r2) && (/^\s*?SA-MC GRADIENT FOR STATE (\d+).1/)){my $x = $1}
  if (($r3) && (/^\s*?SA-MC NACME FOR STATES (\d+).1 - (\d+).1/)){my $x = $1}
 }
},
 mit_qr         => sub {
 open my $in, "< molpro.out" or die "geht nicht\n";
 my ($r1,$r2,$r3) = (1,1,0);
 my $re1 = qr/^\s*?!MCSCF STATE (\d+).1 ENERGY/;
 my $re2 = qr/^\s*?SA-MC GRADIENT FOR STATE (\d+).1/;
 my $re3 = qr/^\s*?SA-MC NACME FOR STATES (\d+).1 - (\d+).1/;

 while (<$in>){
  if (($r1) && (/$re1/)){my $x = $1}
  if (($r2) && (/$re2/)){my $x = $1}
  if (($r3) && (/$re3/)){my $x = $1}
 }
},
 extra          => sub {
 my ($r1,$r2,$r3) = (1,1,0);
 my $re1 = qr/^\s*?!MCSCF STATE (\d+).1 ENERGY/;
 my $re2 = qr/^\s*?SA-MC GRADIENT FOR STATE (\d+).1/;
 my $re3 = qr/^\s*?SA-MC NACME FOR STATES (\d+).1 - (\d+).1/;

 if ($r1){
 open my $in, "< molpro.out" or die "geht nicht\n";
  while (<$in>){
   if (/$re1/){my $x = $1}
  }
 }

 if ($r2){
 open my $in, "< molpro.out" or die "geht nicht\n";
  while (<$in>){
   if (/$re2/){my $x = $1}
  }
 }

 if ($r3){
 open my $in, "< molpro.out" or die "geht nicht\n";
  while (<$in>){
   if (/$re3/){my $x = $1}
  }
 }
},
});

Benchmark: timing 100000 iterations of extra, mit_qr, normal...
     extra: 82 wallclock secs (78.87 usr +  2.58 sys = 81.45 CPU) @ 1227.75/s (n=100000)
    mit_qr: 71 wallclock secs (69.35 usr +  1.29 sys = 70.64 CPU) @ 1415.63/s (n=100000)
    normal: 37 wallclock secs (35.88 usr +  1.27 sys = 37.15 CPU) @ 2691.79/s (n=100000)