$text =~ /sig.*?ma/; # matches sigma and sigima 
                     # (zero or more somethings, non-greedy match)
$text =~ /sig.+?ma/; # matches sigoma and sigilima
                     # (1 or more somethings, non-greedy match)
$text =~ /sig.?ma/;  # matches sigma and sigima, but not sigilima
                     # (zero or 1 something)
$text =~ /sig.ma/;   # just one something