#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw(cmpthese);

my @Patterns=("xxx", "SSS", "s:S");
my %master;

cmpthese(50, {
            orig=>\&getCsvHash1,
            swap=>\&getCsvHash2,
            regex=>\&getCsvHash3,
});

sub getCsvHash1
{
  %master=(); # unset the HASH.
  foreach my $wlp (@Patterns)
  {
    my $key=$wlp;
    $key =~ s/[\s+|:]/_/g;
    open FILE, "csv_file.csv" or die $!;
    while(<FILE>)
    {
      my $line=$_;
      {
        my @csv = split(",", $line);
        if ($csv[1] =~ /"$wlp/)
        {
          push (@{$master{$key}}, $line); # push as value of a hash-
        }
      }
    } #while(<FILE>) ends here
    close FILE;
  } #foreach $wlp ends here
} #Function getWhiteListCsvArrays ends here.

sub getCsvHash2
{
  %master=(); # unset the HASH.
  open FILE, "csv_file.csv" or die $!;
  while(<FILE>)
  {
    my $line=$_;
    foreach my $wlp (@Patterns)
    {
      my $key=$wlp;
      $key =~ s/[\s+|:]/_/g;
      {
        my @csv = split(",", $line);
        if ($csv[1] =~ /"$wlp/)
        {
          push (@{$master{$key}}, $line); # push as value of a hash-
        }
      }
    }
  }
  close FILE;
}

sub getCsvHash3
{
  %master=(); # unset the HASH.
  open FILE, "csv_file.csv" or die $!;
  while(<FILE>)
  {
    my $line=$_;
    my @csv = split(",", $line);

    if ($csv[1] =~ /xxx/) { push @{$master{$1}},  $line; }
    if ($csv[1] =~ /SSS/) { push @{$master{$1}},  $line; }
    if ($csv[1] =~ /s:S/) { push @{$master{s_S}}, $line; }
  }
  close FILE;
}

##</code><code>##

$ time perl pm923771.pl
         Rate  swap  orig regex
swap  0.544/s    --  -47%  -81%
orig   1.03/s   89%    --  -64%
regex  2.87/s  427%  178%    --

real    2m38.179s
user    2m34.503s
sys     0m3.463s