$str = "(<ref links=\" cit314-1 cit314-2 cit314-3 cit314-4 cit314-5\"/>)";

if( $str =~ s/<ref links="(.*?)"(.*?)\/>/
              "<ref links=\"$1\"$2>" . getString($1) . "<\/ref>"/e ){
    print "Match was found." . "\n";
}
print $str . "\n";

sub getString($s){    
    my $s = shift;
    ...more processing of $s...
    return $s;
}