thanks guys... i am new to perl, with all ur suggestions and inputs from perlmonks, i finally came up with this small piece of code ---truthtable.pl

#my $bool_func = "((S0'*B)|((!S0)|A))'";
my $bool_func = "(a'+b'+c')";
#my $bool_func = "((A0)'+A1'+!(a2))'";

# convert the function into equivalent perl expression
$bool_func =~ s/\((\w*)\)'/~($1)/g;     
# to convert the case where variable is represented as (A)' to ~(A)
$bool_func =~ s/(\w*)'/~$1/g;            
# to convert the case where variable is represented as A' to ~A
$bool_func =~ s/(^\(.*\))~$/~($1)/g;    
# to convert the case where expression is (EXPR)' to ~(EXPR)
$bool_func =~ s/!/~/g;             
# to convert the case where not is represented by ! to ~    
$bool_func =~ s/\+/|/g;
$bool_func =~ s/\*/&/g;
(my $perl_expr = $bool_func) =~ s/([a-zA-Z]\w*)/\$val{$1}/g;
## end conversion

print "equivalent expression: $bool_func\n";

# get the variables
my @vars = do {
    my %seen;
    grep !$seen{$_}++, $bool_func =~ /([a-zA-Z]\w*)/g;
};

print "$vars[2],    $vars[1],    $vars[0],    out\n";

# evaluate and print the output
for my $assignment ( 0 .. (2**@vars)-1 ) {
    my %val;
    $val{$vars[$_]} = ( $assignment >> $_ ) & 1
        for 0 .. $#vars;
    my $result = eval $perl_expr & 1;
print join(",    ", map { "$val{$_}" }keys %val),"  =$result\n";
}
[download]

----end--- output---

equivalent expression: (~a|~b|~c)
c,      b,      a,      out
0,      0,      0       = 1
0,      1,      0       = 1
0,      0,      1       = 1
0,      1,      1       = 1
1,      0,      0       = 1
1,      1,      0       = 1
1,      0,      1       = 1
1,      1,      1       = 0
[download]

thanks again

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