You're after something like this:

unless ( $result = my_sub() ) {
   # handle error condition
}
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I've often seen this, which is quite similar:

my $result;
unless ( my_sub(\$result) ) {
   # handle error condition
}
[download]

where &my_sub might look like this:

sub my_sub {
   my $r_result = shift;
   $$r_result = whatever();
   was_there_an_error() ? 0 : 1 ;
}
[download]

andy.