use strict;
use warnings;

my $my_input = 'xxxc=2&xxx1=val1&xxx2=val2';
my @fv_pairs = split /\&/ , $my_input;
my %INPUT;

foreach (@fv_pairs) {
    my ($field, $value) = split /=/, $_, 2;
    
    next unless defined $value;
    $value =~ s/\+/ /g;
    $value =~ s/%(\dA-Fa-f{2})/pack("C", hex($1))/eg;
    $INPUT{$field}=$value;
}

print join "\n", map {"$_ => $INPUT{$_}"} sort keys %INPUT;

##</code><code>##

xxx1 => val1
xxx2 => val2
xxxc => 2