Albeit I concur mostly with FunkyMonk, just for the sake of completeness and something to play with (not everything here presented is a solution, and not even suitable sometimes (some of it is intentionally flawed - one should examine the output before using it); it tries to illustrate to a certain extent what is possible by using map):

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper qw(Dumper);

{
    list_dump(sub {
                      map { $_->[0] < 5 } @{set()}
                  }
              );
    list_dump(sub {
                      map { $_->[2] < 5 ? $_ : () } @{set()}
                  }
              );
    list_dump(sub {
                      map { [ map { $_ + 1 } @$_ ] } @{set()}
                  }
              );
    list_dump(sub {
                      map { local $_ = $_; $_->[0] = 7; $_ } @{set()}
                  }
              );
    list_dump(sub {
                      map { my @copy = @$_; [ map { $_ *= 2 } @copy ] 
+} @{set()}
                  }
              );

    sub list_dump (&) {
        my @list = $_[0]->();
        print Dumper \@list;
    }

    sub set {
        return [ [1,2,3],[4,5,6] ];
    }
}
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