re = /^(?P<artist>.+?(?=\s-\s)) # artist with pos. lookahead
\s-\s # space - space
(?P<title>.+?(?=(?:\(?Feat\.)|$)) # title with pos. lookahead
\(? # optional open parenthesis
(?P<artist2>Feat\.[^()\n]+)? # artist2 with Feat. before
\)? # optional closing parenthesis
(?P<subtitle>.+)?$ # optional subtitle/mx
str = 'Black Coast - Trndsttr
Black Coast - Trndsttr (Feather)
Black Coast - Trndsttr (Lucian Remix)
Black Coast - Trndsttr (Feather) (Lucian Remix)
Black Coast - Trndsttr Feat. M. Maggie
Black Coast - Trndsttr (Feat. M. Maggie)
Black Coast - Trndsttr Feat. M. Maggie (Lucian Remix)
Black Coast - Trndsttr (Feat. M. Maggie) (Lucian Remix)
Black Coast - Trndsttr (Lucian Remix) Feat. M. Maggie
Black Coast - Trndsttr (Lucian Remix) (Feat. M. Maggie)
Black Coast - Trndsttr (Feather) (Lucian Remix) Feat. M. Maggie
Black Coast - Trndsttr (Feather) (Lucian Remix) (Feat. M. Maggie)
Black Coast - Trndsttr (Feather) Feat. M. Maggie (Lucian Remix)
Black Coast - Trndsttr (Feather) (Feat. M. Maggie) (Lucian Remix)
Black Coast - Trndsttr (Feather) (Feat. M. Maggie) Lucian Remix
Black Coast - Trndsttr (Feather) Feat. M. Maggie Lucian Remix
'
subst = '$1 $3 - $2$4'
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