#!/usr/bin/perl -w
use strict;

while (<DATA>) 
{
   chomp;
   my $result = is_match($_);
   defined($result) ? print "$_:\tRESULT=\"$result\"\n"
                    : print "$_:\tRESULT=NO MATCH\n";
}

sub is_match
{
   my $term = shift;
   my $inner = ($term =~ m/^A(.*)Z$/)[0];
   return undef  if (!defined($inner));
   return $inner if $inner eq "";
   return $inner if $inner =~ m/^\s/;
   return undef;
}

=prints:
AZ:	RESULT=""
AZZ:	RESULT=NO MATCH
A SOMETHING Z:	RESULT=" SOMETHING "
ASOMETHINGZ:	RESULT=NO MATCH
A  Z:	RESULT="  "
A ZZ:	RESULT=" Z"
AAZZ:	RESULT=NO MATCH
AA ZZ:	RESULT=NO MATCH
ZA:	RESULT=NO MATCH
=cut

__DATA__
AZ
AZZ
A SOMETHING Z
ASOMETHINGZ
A  Z
A ZZ
AAZZ
AA ZZ
ZA