#! /usr/local/bin/perl -sw
# PARSE LOGICAL EXPRESSIONS TO A "list of lists" PARSE TREE
sub printtree
{
        print "    " x $_[0];
        print "$_[1]:\n";
        foreach ( @_[2..$#_] )
        {
                if (ref($_)) { printtree($_[0]+1,@$_); }
                else         { print "    " x $_[0], "$_\n" }
        }
        print "\n";
}
use Parse::RecDescent;
$RD_AUTOACTION = q{ [@item] };
$grammar =
q{
        expr    :       disj
        disj    :       conj 'or' disj | conj
        conj    :       unary 'and' conj | unary
        unary   :       'not' atom
                |       '(' expr ')'
                |       atom
        atom    :       /[a-z]+/i
};
$parse = new Parse::RecDescent ($grammar);
while (<DATA>)
{
        my $tree = $parse->expr($_);
        printtree(0,@$tree) if $tree;
}
__DATA__
a and b and not c
(c or d) and f