If you use CGI.pm, then there's no need to get messy with regexps: the param and (self_)url function/methods are all you need ...

use CGI qw/ :standard /;

print header;

  # save requested slice
my $slice = param( 'slice' );

  # generate URLs to next 3 slices
for my $offset ( 1..3 ) {
    param( 'slice', $slice + $offset );
    print a( { -href => self_url }, query_string );
}

  # restore original (if needed)
param( 'slice', $slice );

__END__

Query:  slice=31&this=that
Output: slice=32&this=that
        slice=33&this=that
        slice=34&this=that

Query:  this=that&slice=49&that=this
Output: this=that&slice=50&that=this
        this=that&slice=51&that=this
        this=that&slice=52&that=this

Query:  this=that&that=this&slice=5
Output: this=that&that=this&slice=6
        this=that&that=this&slice=7
        this=that&that=this&slice=8
[download]

Season with input validation/error handling to taste. :)

    --k.