$var =1;

{
   my $var = 2;
   print "\$main::var >$main::var<\n";  
   print "\$var >$var<\n"; 
   &show_var;
  # my var doesn't exist outside this scope
}
{
   local $var = 3;
  # local var gives $main::var a temporary value
   print "\$main::var >$main::var<\n";
   print "\$var >$var<\n";
   &show_var;
  # local var ceases to exist when we _leave_ this scope
}
print "\$var >$var<\n";

sub showvar { print "showvar($var)\n"; }