#! /usr/bin/perl
#sample string.
$string = "((2 > 1) | ('word' eq 'toy'))";
#next line converts user-specified operators into Perl
#logical operators. 
$string =~ s/([&|]{1})/$1$1/g;
print "Initial parsed string = $string\n";
#Look ahead assertion.
while ($string =~ /\(((?:[^()])*?)\)/) {
    my $assert = $1;
    my $val = (eval $1) ? 1 : 0;
    print "Case to be evaluated = $1\n";
    print "Evaluated value = $val\n";
    $assert =~ s/\|\|/\\\|\\\|/g;
    $string =~ s/\($assert\)/$val/;
    print "Parsed string = $string\n";
}
print "Result: $string\n";