in reply to Iteration condition...

I don't know about "shorter, more economical", but perhaps easier to maintain:

## a dispatch table in the form state => CODEref my %operation = ( 1 => \&do_this, 0 => \&do_that, 9 => \&do_another_thing, ); ## a table of transitions in the form pattern => state my @transition = ( [ $Start => 1 ], [ $Finish => 0 ], [ $Break => 9 ], ); my $State = 0; # or whatever your initial state is. for my $item (@Input) { # check transition conditions in order; if met, change state for my $trans (@transition) { next unless $item =~ /$trans->[0]/; $State = $trans->[1]; last; } $operation->{$State}->(); # dereference and execute op for this S +tate }

That's a very simple state machine that uses a dispatch table. It's pretty easy to expand: add transitions to the @transition structure, write a sub for each operation and add it to the %operation dispatch table. You don't need to change any other code.

However, if you have a large number of states and/or transitions, using one of the state-machine modules that CountZero references above could be a better choice.

Ramblings and references
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet