#!/usr/bin/perl -wT
use strict;
use CGI;
use Fcntl qw/ :DEFAULT :flock /;
use Data::Dumper;

my $q = CGI->new;
my $log_file = 'some_file.log';
my %params = map { $_, [ $q->param( $_ ) ] } $q->param;

open LOG, ">>", $log_file    or die "Can't open $log_file for appending: $!";
flock LOG, LOCK_EX           or die "Can't get an exclusive lock on $log_file: $!";
print LOG Dumper( \%params ) or die "Can't print to $log_file: $!";
close LOG                    or die "Can't close $log_file: $!";