'.' =~ /./;      # match
'a' =~ /./;      # match
'.' =~ /\Q.\E/;  # match
'a' =~ /\Q.\E/;  # no match

##</code><code>##

$search = '.';
'.' =~ /$search/;      # match
'a' =~ /$search/;      # match
'.' =~ /\Q$search\E/;  # match
'a' =~ /\Q$search\E/;  # no match