use strict;

{

my $a = 1;
my $b = 2;
my $c = 3;

sub f {
  my $var = shift;
  print $var, "=", eval "\$$var", "\n";
};

}

&f("a");
&f("b");
&f("c");

##</code><code>##

$ perl -w a.pl
Variable "$a" is not available at (eval 1) line 2.
Use of uninitialized value in print at a.pl line 11.
a=
Variable "$b" is not available at (eval 2) line 2.
Use of uninitialized value in print at a.pl line 11.
b=
Variable "$c" is not available at (eval 3) line 2.
Use of uninitialized value in print at a.pl line 11.
c=