# Text.
$text = 'Renata';
$window =~ /\b\Q$text\E\b/ism

##</code><code>##

# Uncompiled regexp.
$text = 'Renata';
$regexp = '\\b' . quotemeta($text) . '\\b';
$window =~ /$regexp/ism

##</code><code>##

# Compiled regexp.
$regexp = qr/\b\QRenata\E\b/ism;
$window =~ $regexp