sillymonkeysoftw...@gmail.com <sillymonkeysoftw...@gmail.com> asked:
> I'm working with some customizable data from a config file, and can't
> for the life of me figure out how to test conditionals from an
> external source.
> Does anyone have an idea how to accomplish something like:
>
> my $statement = "1 < 10 and 2 > 10"; # obviously false
> my $result = ($statement) ? 1 : 0; # conditional test
>
> Now, $result will always be true(1), because the conditional is
> really, in effect, just validating that $statement is a defined
> scalar, not testing the statement.
> But, how can I perform an actual conditional statement on this?
> What I really want is:
>
> (1 < 10 and 2 > 10) ? 1 : 0;
You can do something like
my $cond = eval( $statement );
if( $@ ){
# an error occurred while evaluation $statement
#
} else {
# $statement was o.k.; normal program flow
my $result = eval($statement) ? 1 : 0;
# rest of code
}
The two important things to keep in mind:
1) Make sure you sanitize $statement very carefully. Otherwise people can run
arbitrary perl commands and you probably don't want that.
2) Check $@ after calling eval to see wether the code could be executed or
wether it caused an error.
HTH,
Thomas
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