#!/usr/bin/perl
use warnings;
use strict;

use Local::Evaluator qw(evaluate);

system map { Local::Evaluator::evaluate($_) } @ARGV;

##</code><code>##

package Local::Evaluator;

use warnings;
use strict;

use parent 'Exporter';
our @EXPORT_OK = qw( evaluate );

{
    my %HASH;
    $HASH{safe}{bin}   = '/usr/bin';
    $HASH{unsafe}{bin} = '/bin';

    sub evaluate {
        my $word = shift;
        return $word unless 0 == index $word, '#';
        my ($key, $subkey, $rest) = (split /#/, $word, 4)[1 .. 3];
        return $HASH{$key}{$subkey} . $rest if $HASH{$key}
                                            and exists $HASH{$key}{$subkey};
        return $word;
    }
}

__PACKAGE__

##</code><code>##

$ ./evaluate.pl ls -latr \#unsafe#bin#/true
-rwxr-xr-x 1 root root 30204 2010-09-21 20:33 /bin/true
$ ./evaluate.pl ls -latr \#safe#bin#/true
ls: cannot access /usr/bin/true: No such file or directory