Unrecognized escape \Q passed through in regex; marked by <-- HERE in m/\b\Q <-- HERE Renata\E\b/ at -e line 1.
Unrecognized escape \E passed through in regex; marked by <-- HERE in m/\b\QRenata\E <-- HERE \b/ at -e line 1.

##</code><code>##

# ...
print STDERR "/$regexp/\n";
$throw_away = ($window =~ /$regexp/ism) ? 'TRUE' : 'FALSE';
# ...

##</code><code>##

/\b\QRenata\E\b/