use strict;
my $str = 'Headaches, intracranial hypertension, papilledema and exophthalmos may occur with intracranial infiltration.(7-15, 8)
(234---345)';
my $regex = qr/\(([1-9][\d\-\s,]*[0-9])\)/p;
my $subst = '<span class="ref">$1</span>';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html