#!/user/bin/perl
use strict;
use warnings;
use feature 'say';
# use Benchmark qw(:all) ; # WindowsOS
use Benchmark::Forking qw( timethese cmpthese ); # UnixOS

my( %DetailSheet ) =	(
    'ColumnName' => {
	'ID' => {
	    'PositionAdjustment' => 0,
		'RecordName' => 'Identification',
		'RecordNumber' => 0,
		'RecordValue' => '',
		'XlsName' => 'Reference',
		'XlsColumn' => 1,
		'XlsFormat' => '',
		'XlsWidth' => 15,
		'XlsLock' => 1,
		'GuiName' => 'Number',
		'GuiNumber' => 2,
		'GuiValue' => '',
		'Switch' => [
		    ['O','0'],
		    ['l','1']
		]
	},
	    'DESCRIPTION' => {
		'PositionAdjustment' => 0,
		    'RecordName' => 'Description',
		    'RecordNumber' => 1,
		    'RecordValue' => '',
		    'XlsName' => 'Description',
		    'XlsColumn' => 2,
		    'XlsFormat' => '',
		    'XlsWidth' => 15,
		    'XlsLock' => 1,
		    'GuiName' => 'Description',
		    'GuiNumber' => 3,
		    'GuiValue' => '',
		    'Switch' => [
			[' AND ', ' & '],
			[' WITH ', ' W/ ']
		    ]
	}
    }
    );

sub getKeyByIteration {
    my ( $DetailSheet ) = @_;
    for my $key ( keys %$DetailSheet ) {
	for my $secondLevelKeys ( keys %{ $DetailSheet->{$key}} ) {
	    while (my ($key, $value) = each %{ $DetailSheet->{$key}{$secondLevelKeys} }) {
		return $secondLevelKeys if ($key eq 'XlsColumn' && $value == 2);
	    }
	}
    }
}

# say getKeyByIteration(\%DetailSheet);

sub getKeyByGrep {
    my ( $DetailSheet ) = @_;
    return grep { $DetailSheet{ColumnName}{$_}{XlsColumn} == 2 }
    keys %{$DetailSheet{ColumnName}};
}

# say getKeyByGrep(\%DetailSheet);

my $results = timethese(100000000, { Grep => \&getKeyByGrep,
				     ForEach => \&getKeyByIteration, }, 'none');
cmpthese( $results );

__END__

$ perl test.pl
             Rate    Grep ForEach
Grep    1972776/s      --    -51%
ForEach 4011231/s    103%      --