Not extensively tested, but does 
my @strings = ('AZ', 'A SOMETHING Z', 'ASOMETHINGZ', 'A  Z', 'A ZZ', '
+AA ZZ', 'AAZZ');

for (@strings) {
    if (/A( .*?)?Z/) {
        my $grabbed = $1 // '';
        say "'$_' grabbed '$grabbed'";
    }
    else { say "'$_' did not match" }
}
__END__
'AZ' grabbed ''
'A SOMETHING Z' grabbed ' SOMETHING '
'ASOMETHINGZ' did not match
'A  Z' grabbed '  '
'A ZZ' grabbed ' '
'AA ZZ' grabbed ' '
'AAZZ' grabbed ''

[download]

do what you want?

Update

What should 'A ZZ', 'AAZZ' and 'AA ZZ' match? (added these as test cases)

Unless I state otherwise, all my code runs with strict and warnings

In reply to Re: This regexp made simpler by FunkyMonk
in thread This regexp made simpler by rovf

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