re = /^([^,]+?), ([^-&]+?) & ([^,]+?), ([^-]+) -/m
str = 'Aaranovitch, Ben - Peter Grant 01 - Die Fluesse von London.epub
Abbie, Taylor - Denn niemand wird dir glauben.epub
Aiken, G. A. - Drachenwandler 01 - Dragon Kiss, Drachen Kuss.epub
Achilles, Achim & Joung, Frank - Laufen und Trainieren.epub
'
subst = '$2 $1 & $4 $1 -'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
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 Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html