re = /^/mi
str = '"Cliente1\\\\Rem\\\\COB0111111.REM.txt"
"Cliente1\\\\Rem\\\\23123123.REM.txt" 
"Cliente1\\\\OK\\\\COB02222222.REM.txt" 
"Cliente1\\\\Ret\\\\COB0613062019.REM.txt"
"COB0613062019.REM.txt" 
"Cliente2\\\\COB0613062019.REM.txt"
"Cliente2\\\\Rem\\\\COB0633333.REM.txt"
"Cliente2\\\\Rem\\\\pasta2\\\\COB02123123.REM.txt"
"Cliente2\\\\Bla\\\\Rem\\\\COB0613062019.REM.txt"
"Cliente1\\\\COB0613062019.REM.txt"
"Rem\\\\COB0613062019.REM.txt" 
"Rem"
"Cliente3"'
# Print the match result
str.scan(re) do |match|
    puts match.to_s
end
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