#! /usr/local/bin/perl -sw
# PARSE LOGICAL EXPRESSIONS
use Parse::RecDescent;
$grammar =
q{
expr : disj no_garbage
no_garbage: /^\s*$/
| <error: Trailing garbage>
disj : conj ('or' conj)(s?)
conj : unary ('and' unary)(s?)
unary : 'not' atom
| '(' expr ')'
| atom
atom : /<.+?>/
};
$parse = new Parse::RecDescent ($grammar);
$input = '';
print "> ";
while (<>)
{
if (/^\.$/) { defined $parse->expr($input) or print "huh?\n"; $input = '' }
else { $input .= $_ }
print "> ";
}