Esteemed Monks,

Thus far you have all been extraordinarily helpful in my experiences with Perl and I have to once again ask for your assistance.

I have some code that I need to run, but I only want to write it once. I know that I can enclose is in subroutines like such: 

if ($opt{'c'}) {
 open CATLOG, "<$MAILLOG";
 while (my $line = <CATLOG>) { while_sub($line); }
} else {
 $log = File::Tail->new( name => $MAILLOG, tail => -1);
 while (defined(my $line=$log->read)) { while_sub($line); }
}

[download]

For my own coding style and the program flow and readability, I would prefer to do something like is below, however I know that this won't work (syntactically), but I believe it illustrates my goal. I want to just go through the file once (cat it) if $opt{'c'} is set, otherwise I want to tail it (using File::Tail). 

if ($opt{'c'}) {
 open CATLOG, "<$MAILLOG";
 while (my $line = <CATLOG>) {
} else {
 $log = File::Tail->new( name => $MAILLOG, tail => -1);
 while (defined(my $line=$log->read)) {
}
 ...while loop code here...
 } # End while loop
close (CATLOG) if ($opt{'c'});

[download]

I am pretty sure that it would have something to do with BLOCK: { } expressions (even though I am not sure how to structure it) or potentially working an eval statement in there. Help. Thanks.

UPDATE:Thanks to all who helped. The key to this was tie. I now have it written as follows: 

 if ($opt{'c'}) {
   open MAILLOG_R, "<$MAILLOG"
     or die("Unable to open mail log: $!\n");
 } else {
   tie *MAILLOG_R, 'File::Tail', (name => $MAILLOG, tail => -1);
 }

 while(my $line = <MAILLOG_R>) {
  ...blah...
 }

[download]

Note: The reason I use MAILLOG_R is because, using another PM, I tie *MAILLOG_W for consistancy.

In reply to Looping based on a Conditional by madbombX

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