http://play.inginf.units.it/#/level/1
\d+
http://play.inginf.units.it/#/level/2
(\w+)(\:\w+){5}
(\w+:){5}\w+
http://play.inginf.units.it/#/level/3
ftp://ftp\d?\d?\.?\w?\w?\.FreeBSD\.org/pub/FreeBSD/
ftp:\S+
http://play.inginf.units.it/#/level/4
\$.+?\$
http://play.inginf.units.it/#/level/5
\d+(\.\d+)+
(\d+\.){3}\d+
http://play.inginf.units.it/#/level/6
href=(['"]).+?\1
http://play.inginf.units.it/#/level/7
http://[\S]+(?:(?=\s|\.|\>))
(Not Working)
http://[^ >]+[\w/]
http://play.inginf.units.it/#/level/8
<h(\d)>?.+</h\1>
http://play.inginf.units.it/#/level/9
\(?\d{3}\)?.\d{3}.\d{4}
\(?\d+\)?[ -./]\d+[-.]\d+
http://play.inginf.units.it/#/level/10
\w+\,\s.+?\w+
(Not Working)
(?<=[{ ])\w+(-\w+)?,( [A-Z]\w*(({.+?}|')\w+)?)+
http://play.inginf.units.it/#/level/11
(?<=<h(\d)>).+?(?=</h\1>)
(Not Working)
(?<=<h(\d).*?>).+(?=</h\1>)
http://play.inginf.units.it/#/level/12
(?<=\d+\.\s)\w+\,\s[\.\w]+(?=[\,\:])
(?<=\. )\w+, (.\.)+
My solution, the i-th row is the solution to the i-th problem :
\d+
\w+:\w+:\w+:\w+:\w+:\w+
ftp:[^\s]+
[$][^$]+[$]
\d+[.]\d+[.]\d+[.]\d+
href=["'][^\s]+["']
http://\S+(/|\w)
<h\d.+
(\d+[/.-]\d+[/.-]\d+)|([(]\d+[)]\s\d+-\d+)
((?<=and\s)|(?<={))+?[\w-']+,.+?((?=\sand)+?|[}]nter|(?=})+?)
(?<=<h.+?>).+(?=</h\d>)
(?<=\d+.\s)\w+,\s\w.(\w.)?(\w.)?(?=[,:])