Tough problem. You could try a queue - the idea is to store
those keys whose values are not complete, and keep
substituting until they are complete:
use strict;
use Data::Dumper;
my (%hash,@queue);
while (<DATA>) {
chomp;
if (/^#DEFINE\s+<([^>]+)>\s+(.*)/) {
$hash{$1} = $2;
}
}
do_it($_) for keys %hash;
do_it(shift @queue) while @queue;
sub do_it {
my $key = shift;
$hash{$key} =~ s/<([^>]+)>/$hash{$1}/g;
unshift @queue, $key if $hash{$key} =~ /</;
}
print Dumper \%hash;
__DATA__
------------------
#DEFINE <PATH> /path/to/something
#DEFINE <VERSION> v12<REV>
#DEFINE <REV> 3
#DEFINE <FILE> <PATH>/foo_<VERSION>.txt
BUT!!! This is going to loop infinitely if you have one
single circular reference in your #DEFINE statements. For
example, change <VERSION> to:
#DEFINE <VERSION> v12<REV><FILE>
and this will not work. Hopefully someone else will have
a better answer, but if you are %110 certain that this will
not be the case, then this code will prevent unecessary
iterations.
p.s. this might be a job for Parse::RecDescent ...
UPDATE: danger++ and sfink++
jeffa
L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)