Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Howdy Monks,

I'm trying to get my head around variable interpolation and dereferencing, and all I can say is that I have a headache ;)

Can Perl use the value of one variable as the name of another variable?

For example: 

#!/usr/bin/perl -w
use strict;
my ( @Category, @Cat1, @Cat2, @Cat3, $Sub_Category, $Value );

@Cat1 = qw( a b c );
@Cat2 = qw( 1 2 3 );
@Cat3 = qw( x y z );

@Category = qw( Cat1 Cat2 Cat3 );

foreach $Sub_Category (@Category) {
  print "$Sub_Category\n";

  foreach $Value (@$Sub_Category) { # I'm trying to make Perl see @Cat
+1 but, Larry gives me the following error: "Can't use string ("Cat1" 
+as an ARRAY ref while "strict refs" in use"
    print "$Value\n";
  }
}

__END__

[download]
I apologize for the ambiguous code but, I don't have a real world need for this, I'm just trying to answer questions that sprung up while taking a shower.

Many Thanks!

Replies are listed 'Best First'.
Re: Dynamic Variables?
by dragonchild (Archbishop) on Feb 28, 2002 at 21:46 UTC
    Use multi-level data structures instead. Do something like: 
    my %Categories = (
   cat1 => [
      'a', 'b', 'c',
   ],
# etc...
);

foreach my $sub_category (sort keys %Categories) {
   print $sub_category, $/;
   foreach my $value (@{$Categories{$sub_category}}) {
      print "\t$value\n";
   }
}

__END__

    [download]

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[reply]
[d/l]
      dragonchild, thanks! That has the effect I was thinking of.
[reply]
Re: Dynamic Variables?
by patgas (Friar) on Feb 28, 2002 at 22:07 UTC

    The short answer is, 'yes, Perl can use the value of one variable as the name of another variable', and I realize you're just curious, but dear God don't ever use this in real code. Here's a whole page about it: http://perl.plover.com/varvarname.html

    "We're experiencing some Godzilla-related turbulence..."

[reply]
      patgas, thanks!

         This is why I love sites like Perl Monks! Instead of getting RTFM, or other newbie blow offs, you all (ok, most) provide thoughtful answers. And best of all, if it's a matter of opinion or TMTOWTDI, you offer reasoning to back it up.
[reply]

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