$useragent =~ s{ ( [+] ) [[] [^]]+ []] ( [+] ) }{$1$2}msx;

##</code><code>##

$useragent =~ y{+}{ };

##</code><code>##

$ ver_overload_prob.pl
UA: Mozilla/4.06+[en]+(WinNT;+I)
Netscape
4.060
Windows NT
UA: Opera/9.80 (Windows NT 5.1; U; en) Presto/2.6.30 Version/10.61
Opera
10.610
Windows XP
UA: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.1.4) Gecko/20091016 Firefox/3.5.4
Firefox
3.005004
Windows XP
UA: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/525.28 (KHTML, like Gecko) Version/3.2.2 Safari/525.28.1
Safari
3.002002
Windows XP
UA: Mozilla/5.0+(Windows;+U;+Windows+NT+5.1;+en-US;+rv:1.9.1.15)+Gecko/20101026+Firefox/3.5.15+(.NET+CLR+3.5.30729)
Firefox
3.005015
Windows XP

##</code><code>##

    $v    =~ s{
                pre      |
                rel      |
                alpha    |
                beta     |
                \-stable |
                gold     |
                [ab]\d+  |
                a\-XXXX  |
                \+
                }{}xmsig;

##</code><code>##

    $v    =~ y{+}{ };
    $v    =~ s{
                pre      |
                rel      |
                alpha    |
                beta     |
                \-stable |
                gold     |
                [ab]\d+  |
                a\-XXXX
                }{}xmsig;