#!/usr/bin/env perl5
use strict;
use warnings;

my @clients;
my %tmp;

while(<DATA>)
{
	chomp;

	# Assume a format of "Type Data"
	my ($type, $data) = split / /;

	# If it's a MAC address, save off our pre-existing record (if any),
	# and start a new one.
	if($type eq "MAC")
	{
		if(keys %tmp)
		{
			# Have to unroll a copy here, otherwise the next line empties
			# it out.
			push @clients, { (%tmp) };
			%tmp = ();
		}

		$tmp{MAC} = $data;
	}

	# RSSI and SNR just get saved
	$tmp{RSSI} = $data if $type eq "RSSI";
	$tmp{SNR} = $data  if $type eq "SNR";
}

# Save the 'last' one if we fell off the end
push @clients, \%tmp if keys %tmp;

# Show it
use Data::Dumper; print Dumper \@clients;

# Find a given entry
sub showmacsnr
{
	my $mac = shift;
	my @ba = grep { $_->{MAC} eq $mac } @clients;

	if(@ba)
	{
		my $ent = $ba[0];
		print "MAC $mac has SNR $ent->{SNR}\n";
	}
	else
	{
		print "Can't find MAC $mac\n";
	}
}

showmacsnr("ba:98:76:54:32:10");
showmacsnr("thi:is:is:nt:re:al");


# Sample data
__DATA__
MAC 01:23:45:67:89:ab
RSSI 12
SNR 18
MAC ba:98:76:54:32:10
RSSI 7
SNR 3

##</code><code>##

% ./tst.pl 
$VAR1 = [
          {
            'RSSI' => '12',
            'SNR' => '18',
            'MAC' => '01:23:45:67:89:ab'
          },
          {
            'SNR' => '3',
            'RSSI' => '7',
            'MAC' => 'ba:98:76:54:32:10'
          }
        ];
MAC ba:98:76:54:32:10 has SNR 3
Can't find MAC thi:is:is:nt:re:al