You seem to be missing at least two close curly brackets, one after the while loop and one after the if statement before the alarm.

You return undef on error, so the final statement might be better written as:
print "Collected $file (rc=". (defined $rc?$rc:'undef') . ")\n";
You are mixing stdout (bare print) and stderr (die) messages. I suggest you only print error messages to stderr, use print STDERR, or warn, or incorporate into the die statement that follows.

Your while loop could be simplified in a number of ways. For example:

while (my $line = <FILE>) {
         chomp $line;
         push @$outref, $line;
   # for test purposes - make it timeout!
         sleep 5;
         $outbytes += length($line);
         if ($outbytes >= $g_max_file_size) {
            warn "Maximum file size reached after $outbytes bytes";
            last;
         }
   }
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Assuming I put the close braces in the right place.
Another approach might be to avoid the loop altogether by testing the file size before you start reading:

   my $file_size = -s IFILE;
   die "$file too large at $file_size bytes" if $file_size > $g_max_fi
+le_size;
  @$outref = <IFILE>;
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