I really ought to be able to answer this for myself but it's turning out to be a long week and what's left of my brain is half-fried already.

Anyway, all I want to do is declare a global variable in the main part of my programand then manipulate it within subroutines.

This fragment shows what I am trying to do. But it fails when I try to increment the value withing the sub "modification of a read-only value..."

#/usr/bin/perl
$tt = 1;
mt($tt);

sub mt {

  my $t = shift;
  print " sub: 1 t = ${$t}\n";
  ${$timer}++;
  print " sub: 2 t = ${$t}\n";

}

[download]

Once I have understood (with someone's help, hopefully) what I need to do to make this work, I'd like to ensure it works with "use warnings, strict" and with sub prototyping... and anything else I can think of the keep it under some sort of control.

As I said, I should be able to do this by now. I have worked on PHP code for too long I guess!

Thanks for any help

Bill

Update

Whoopsy! Yes, I did mean $t throughout. This is just the simplest code I could write off the fly to try and demonstrate what I am trying to do. I always use strict and warnings in my "proper" code - this is just some QnD to demo my problemette.

The reason I can't use it as a "real" global and deal with it directly in the subroutine is that I have x number or variables to maintain with values, not just the one in this example. And I do like to use subroutine prototyping

But thanks for the replies... I can now see where I was screwing up and I am happier now I understnad why I was screwing up. Still not entirely sure this is The Right Way To Program tho'! :-)

Bill

In reply to global, write-able vars by zeltus

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