Here is a super-simple OO framework for you.

Processor.pm

package Processor;

# constructor in base class only

sub new {
  my $pkg = shift;
  bless {}, $pkg;
}

# init, process, finish in subclasses

1;
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Processor/SomeSubClass.pm

package Processor::SomeSubClass;

@ISA = ( Processor );

sub init {
  my $self = shift;
  # do something
}

# should be called process_line
# this one upcases it
sub process {
  my $self = shift;
  my $line = shift;
  return uc( $line );
}

sub finish {
  my $self = shift;
  # do something
}

1;
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The script that runs it:

#!/usr/bin/perl

use Processor;
use Processor::SomeSubClass;

my $p = Processor::SomeSubClass->new();

$p->init;
while (<>) {
  print $p->process( $_ );
}
$p->finish;
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I'm not totally sure if this is what you intended - init and finish coming before and after processing all the lines for example - but it should get you going if you havent't done it before.

Note that my examlpe does not store any of the data in the object - again, because its hard to see what problem you are going to be solving.

qq