From: Gavin Sinclair [mailto:gsinclair / gmail.com] 
# On Aug 3, 5:58 pm, Peñá, Botp <b... / delmonte-phil.com> wrote:
# > min = list.sort!{|a,b| a.size <=> b.size}.first
# > break if list.all?{|a| a =~ /^#{min}/} while min.chop!
# I just realised that the solution I just posted elsewhere in this
# thread is very very similar to this one.
# Be careful that using bang methods in chains is sometimes problematic,
# as they can return nil if nothing changes (sort! doesn't have this
# problem).  

indeed. as long as the array has no nil elements, w're ok w sort!

irb(main):009:0> s="test"
=> "test"
irb(main):010:0> s.downcase!.downcase!
NoMethodError: undefined method `downcase!' for nil:NilClass
        from (irb):10
        from :0
irb(main):011:0> a=[1,1,1]
=> [1, 1, 1]
irb(main):012:0> a.sort!.sort!
=> [1, 1, 1]

i realized just now that i posted the first code.  That should be,

min = list.sort!{|a,b| a.size <=> b.size}.shift  # <--shift instead of first
break if list.all?{|a| a =~ /^#{min}/} while min.chop! 

but anyway, after a couple of tests, the sort does not help much, so

min = list.min{|a,b| a.size <=> b.size}
break if list.all?{|a| a =~ /^#{min}/} while min.chop! 

hmm..  Gavin, your until code just gave me a hint. if we reverse logic, we can save the break and make it more readable too.

min = list.min{|a,b| a.size <=> b.size}
min.chop! until list.all?{|a| a =~ /^#{min}/}

and we can use switch w #any? anytime too :)

min = list.min{|a,b| a.size <=> b.size}
min.chop! while list.any?{|a| a !~ /^#{min}/}

ruby power, indeed.

kind regards -botp