dereference question

Randal L. Schwartz merlyn at
Sun Mar 9 10:56:27 CST 2003

>>>>> "Joel" == Joel Fentin <joel at> writes:

Joel> In my application, both line 1 and line 2 seem to do the same job,
Joel> thus
Joel> revealing the value contained within. But they won't work for $E or
Joel> $F. Is
Joel> there a line of code which will apply to all referenced scalars that
Joel> are
Joel> read in from the file?
>> Hmm.  Sounds like a FAQ to me.  Did you check the FAQs first?

Joel> I tried everything I could think of. I read everything I could think of.
Joel> Which specific FAQ do you have in mind?

$ perldoc -tq variables

Found in /usr/libdata/perl5/pod/perlfaq4.pod
  How can I expand variables in text strings?
            Let's assume that you have a string like:

                $text = 'this has a $foo in it and a $bar';

            If those were both global variables, then this would suffice:

                $text =~ s/\$(\w+)/${$1}/g;  # no /e needed

            But since they are probably lexicals, or at least, they could
            be, you'd have to do this:

                $text =~ s/(\$\w+)/$1/eeg;
                die if $@;                  # needed /ee, not /e

            It's probably better in the general case to treat those
            variables as entries in some special hash. For example:

                %user_defs = ( 
                    foo  => 23,
                    bar  => 19,
                $text =~ s/\$(\w+)/$user_defs{$1}/g;

            See also ``How do I expand function calls in a string?'' in this
            section of the FAQ.

Found in /usr/libdata/perl5/pod/perlfaq7.pod
  How can I catch accesses to undefined variables/functions/methods?
            The AUTOLOAD method, discussed in "Autoloading" in perlsub and
            "AUTOLOAD: Proxy Methods" in perltoot, lets you capture calls to
            undefined functions and methods.

            When it comes to undefined variables that would trigger a
            warning under "-w", you can use a handler to trap the
            pseudo-signal "__WARN__" like this:

                $SIG{__WARN__} = sub {

                    for ( $_[0] ) {         # voici un switch statement 

                        /Use of uninitialized value/  && do {
                            # promote warning to a fatal
                            die $_;

                        # other warning cases to catch could go here;

                        warn $_;


Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn at> <URL:>
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