re = /(.*?),(.*)/m
str = 'Geranium, Ivy
Geranium, Zonal
Geranium, Interspecific
Impatiens, New Guinea
Petunia, Trailing
Petunia, Spreading
Petunia, Miniature Trailing
Impatiens, Interspecific New Guinea
Mum, Garden
Mum, Pot
Combinations, Vigorous'
subst = '\\2 \\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