On Tuesday 08 Dec 2009 11:03:44 Anders Hartman wrote:
> Jeff Pang skrev:
> > Anders Hartman:
> >> Hello,
> >>
> >> I which to use eval to execute subroutines dynamically.
> >>
> >> The following code snippet fails:
> >>
> >>
> >> #!/usr/bin/perl
> >>
> >> use strict;
> >> use warnings;
> >>
> >> sub asub {
> >> our $abc;
> >> print $abc;
> >> }
> >>
> >> my $abc = "abc\n";
> >> eval "asub";
> >> exit 0;
> >
> > I don't think you want an eval here.
> >
> > use strict;
> > use warnings;
> >
> > our $abc = "abc\n";
> >
> > sub asub {
> > print $abc;
> > }
> >
> > asub;
> >
> >
> > Also you may want to know something about Perl's variable scope, see:
> > http://perl.plover.com/FAQs/Namespaces.html.en
>
> Thanks for the link above.
> However, I DO need to use eval because the names of the functions to call
> are determined dynamically at runtime.
> A solution has been found: If I change the line
>
> my $abc = "abc\n";
>
> in the main program to
>
> our $abc = "abc\n";
>
> everything works. I don't quite see why though ;-)
>
That's because our is a package-scope variable and your previous my is a
lexical variable that just happens to live in the global scope. See:
http://perl.plover.com/FAQs/Namespaces.html
Regarding using string eval "" - you can do the same using UNIVERSAL::can,
which would be safer in this case:
<<<<
__PACKAGE__->can("asub")->(@params);
>>>>
Perl is a symbolic language. :-)
eval "" has some legitimate uses, though, but you should be very cautious with
it.
Regards,
Shlomi Fish
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