My first inclination would be to reformat the data into something that could be read by DBD::AnyData (or just stuff it into a db), then convert your filter into SQL. The former looks pretty easy given your example. The latter is probably quite a bit trickier.

Without more information about how many filters (queries) you have, how complex and dynamic they are, how many times you're running them, etc, though, this may not be the best solution. I'm sure other monks will provide lots of other WTDI.

Well, for now, I'll just get it working with a two level filter (Two for OR and Two for AND)... And thanks for the suggestion, will look into it now...

Cos the problem intrigued me :)

#! perl -slw
use strict;

## Convert query syntax to evalable Perl code
sub buildQuery {
    local $_ = uc shift;
    while( m[ \( (?: AND | OR ) | != | = ]x ) {

        s< ( [^!=()\s]+ ) ( != | = ) ( [^()\s]+ ) >{
            my $op = ( $2 eq '!=' ? 'ne' : 'eq' );
            "[\$\L$1\E $op '$3']";
        }xge;

        s< \( \s* ( AND ) \s+ ( \[ [^()]+ \] ) \s+ ( \[ [^()]+ \] ) \s
+* \) >
        { "[$2 && $3]" }xge;

        s< \( \s* ( OR ) \s+ ( \[ [^()]+ \] ) \s+ ( \[ [^()]+ \] ) \s*
+ \) >
        { "[$2 || $3]" }xge;
    }
    tr/[]/()/;
    return $_;
}

## Read data and UPPER case
my $data = do{ local $/; uc <DATA> };

## Some variables
my( $author, $profit, $publisher, $book );

## And a regex to populate them from each record
my $re = qr[
    PAGE        \s+ \d+ \s+
    AUTHOR:     \s+ ( [^\n]+ ) (?{ $author    = $^N }) \s+
    PROFIT:     \s+ ( [^\n]+ ) (?{ $profit    = $^N }) \s+
    PUBLISHER:  \s+ ( [^\n]+ ) (?{ $publisher = $^N }) \s+
    BOOK:       \s+ ( [^\n]+ ) (?{ $book      = $^N }) \s+
]x;

## Covert the query NOTE: (AND ) syntax is required
## where example used implicit AND
my $query = buildQuery( <<EOQ );
(AND
    (OR
        (AND AUTHOR=John PROFIT=90% )
        (AND AUTHOR=Matt PROFIT=80% )
    )
    PUBLISHER=OReilly
)
EOQ
print "\nQuery: $query\n";

## Test the condition and print the record if it matches
## For each record
eval "$query" and print $1 while $data =~ m[ ( $re ) ]xg;

## Same again for another query
## Note != also accepted.
my $query2 = buildQuery( <<EOQ );
(OR
    (AND AUTHOR=John PROFIT!=90% )
    (AND AUTHOR=Matt PUBLISHER!=OReilly )
)
EOQ
print "\nQuery: $query2\n";

eval "$query2" and print $1 while $data =~ m[ ( $re ) ]xg;


__DATA__
Page 1

AUTHOR: John
PROFIT: 20%
PUBLISHER: TMH
BOOK: OPERATING SYSTEMS

Page 2

AUTHOR: John
PROFIT: 90%
PUBLISHER: OREILLY
BOOK: ALGORITHMS

Page 3

AUTHOR: Matt
PROFIT: 80%
PUBLISHER: TMH
BOOK: COMPUTER NETWORKS

Page 4

AUTHOR: Matt
PROFIT: 80%
PUBLISHER: OREILLY
BOOK: COMMUNICATION SYSTEMS
[download]

Outputs:

[ 9:25:03.05]C:\test>670477

Query: (((($author eq 'JOHN') && ($profit eq '90%')) || (($author eq '
+MATT') && ($profit eq '80%'))) && ($publisher eq 'OREILLY'))


PAGE 2

AUTHOR: JOHN
PROFIT: 90%
PUBLISHER: OREILLY
BOOK: ALGORITHMS


PAGE 4

AUTHOR: MATT
PROFIT: 80%
PUBLISHER: OREILLY
BOOK: COMMUNICATION SYSTEMS


Query: ((($author eq 'JOHN') && ($profit ne '90%')) || (($author eq 'M
+ATT') && ($publisher ne 'OREILLY')))


PAGE 1

AUTHOR: JOHN
PROFIT: 20%
PUBLISHER: TMH
BOOK: OPERATING SYSTEMS


PAGE 3

AUTHOR: MATT
PROFIT: 80%
PUBLISHER: TMH
BOOK: COMPUTER NETWORKS
[download]

Bravo! :)

Another approach: assuming, that we can "upgrade" filter a little

$_=<<END_OF_FILTER;
(AND
  (OR
    (AND
      (COND AUTHOR=John)
      (COND PROFIT=90%)
    )
    (AND
      (COND AUTHOR=Matt)
      (COND PROFIT=80%)
    )
  )
  (COND PUBLISHER=OReilly)
)
END_OF_FILTER

%hash = (
    AUTHOR=> 'John',
    PROFIT=> '90%',
    PUBLISHER=> 'OReilly',
    BOOK=> 'OPERATING SYSTEMS'
);

sub AND
{
    print "and debug: [@_]";
    for(@_)
        { return 0 if ! $_ }
    return 1
}
    
sub OR
{
    print "or debug: [@_]";
    for(@_)
        { return 1 if $_ }
    return 0
}
    
sub COND
{
    my ($key, $value)=@_;
    $ret = 0 | ($hash{$key} eq $value);
    print "cond debug: @_ -> $ret";
    return $ret
}

# add comas between ) and ( braces
s/\)(\s*)\(/),$1(/g;

# convert COND a little - I hope you do not have O'reilly name... :)
s/\(COND (\w+)=([^)]+)\)/(COND '$1','$2')/g;

# we have proper parens already, move it only
s/\((AND|OR|COND)\b/$1(/g;

# see how it looks now
print $_;

# and voila!
print "ok" if eval;
[download]

Update: The question is only how to add (COND ...) block with one regexp to original filter? Search for '=' like this?

s/\w+=\S+/(COND $&)/g
[download]

Or there can be whitespace in some values, on which regexp fails? As only legend knows the format of conditions, the answer and a good regexp is in the legend :)

Maybe it would be worth writing piece of code converting this filter into something more perlish like this?:

(
  (
    ($hash{AUTHOR} eq 'John' and $hash{PROFIT} eq '90%')
or
    ($hash{AUTHOR} eq 'Matt' and $hash{PROFIT} eq '80%')
  )
and
  $hash{PUBLISHER} eq 'OReilly'
)
[download]

Then your filter is just a Perl condition, which you can apply to your input data stored in %hash like this:

%hash=(
AUTHOR=> 'John',
PROFIT=> '20%',
PUBLISHER=> 'TMH',
BOOK=> 'OPERATING SYSTEMS'
)
[download]

BTW. It is not good, that two conditions (AUTHOR=John PROFIT=90%) are separated by space, should be separated with (AND ...).

        print $db_title."\n";
    print $db_source."\n";
    print $db_length."\n";
    print $db_author."\n";
    print $db_body."\n";
    print $db_language."\n";
    print $db_subject."\n";
    print $db_datepub."\n";
    print $db_loaddate."\n";
    print "\n\n\n";
[download]

my $query = buildQuery( <<EOQ );
    (OR
        (OR AUTHOR=John Nash PROFIT=90% )
        (OR AUTHOR=Matt PROFIT=80% )
    )
EOQ
print "\nQuery: $query\n";
[download]