does_work.rb

patterns = []
patterns << ".pdf"
puts patterns

matches = []
Find.find('./') do |match|
  patterns.each do |pattern|
    matches << match if match =~ /.*\.pdf$/
  end
end

puts matches

doesn't_work.rb

patterns = []
patterns << ".pdf"
puts patterns

matches = []
Find.find('./') do |match|
  patterns.each do |pattern|
    matches << match if match =~ /.*\#{pattern}$/ # /.*\.pdf$/
  end
end

puts matches