Playing with the Firefox session file...

json.pl

#!/usr/bin/perl -w
use strict;
use diagnostics;
use JSON;
use Data::Dumper;

my $sessionstore = '/home/martin/.mozilla/firefox/12345678.default/sessionstore.js';

my $json_raw;
open my $fh_in, "<$sessionstore" or die "Can't open $sessionstore: $!\n";
while (<$fh_in>){
	$json_raw .= $_;
}

my $json = JSON->new->utf8;
my $json_cooked = $json->decode($json_raw);
my @windows = @{$json_cooked->{'windows'}};

foreach my $window (@windows){
	my $tabs = $window->{'tabs'};
	print Dumper($tabs);
}