die / exit / style question

[Ela Jarecka]

Hi folks,
I have a couple of doubts/questions about the usage of above functions:

1. will those three always work the same ( I have troubles understanding the
'die' description in Llama book ( $!, $?>>8, the status of the last reaped
child from a system, wait, close on a pipe, or `command`))?:

if ( ( $reqrec->fillServ($ServRef) ) == undef ) {
   print "fillRec failed! \n";
   exit;
}

if ( ( $reqrec->fillServ($ServRef) ) == undef ) {
   die "fillRec failed! \n";
}

$reqrec->fillServ($ServRef) or die "fillServ failed";

In fillServ function, I use 'return;' upon failure and 'return 1;' if
everything is OK. 

2. is it a matter of style to use 'not defined(_expression_)' or
(_expression_) == undef? I get warnings in the second case..
Will defined cover also an empty string?

Any comments will be greatly appreciated, as it is my first bigger program
in Perl and I would like it to work flawless...

Ela