$branch =~ /^([\w-]+)$/i;
$branch = $1;

if ($sourcefile =~ /([\w .-]+)$/i) {;     #strip off path stuff
   $newfile = $1;
} else {
   return("Bad file name");
}

open (OUTFILE, ">../$branch/images/$newfile") or die "Cannot open $newfile: $!";
...