Re: how to check syntax of code inside a scalar?

[tilly]

If you want the check to be right, then no. Nothing but perl can parse Perl.

However Perl::Tidy does a usually acceptable job of figuring out Perl syntax.

[tjking]

Uggh, it's a bit shortsighted that there's no built-in function for this. However, after playing a bit, I've found that this can be simulated without having to actually execute the scalar's contents by pre-pending "return;" and testing with eval:

sub syntax_ok {
        my $source = "return;\n" . shift;
        eval $source;
        return 1 unless $@;
        return 0;
}

Thanks!

[Crackers2]

Bad idea... try it with this:

syntax_ok(qq{BEGIN { print "yay\n"; }});

and you'll see that the BEGIN block still gets run, bypassing your return statement. So I'd consider it rather unsafe.

[snoopy]

This does however seem to match the perl -c syntax check. From perlrun:

       -c   causes Perl to check the syntax of the program and then exit
            without executing it.  Actually, it will execute "BEGIN",
            "UNITCHECK", "CHECK", and "use" blocks, because these are
            considered as occurring outside the execution of your program.
            "INIT" and "END" blocks, however, will be skipped.

perl -c -e 'BEGIN { print "yay\n"; }; print "boo\n"'

yay
-e syntax OK