@wetransfer_fix = map { (my $t = $_) =~ s/\.tif//; $t } grep # ...as before...

##</code><code>##

unless( chdir( $wetrasnfer ) ) {
  my $chdir_error = $!;  ## In case mail() clobbers old value
  mail( ... blah ... );  ## send email notification
  die qq{Couldn't send error mail: $chdir_error\n};
}