From: globalrev [mailto:skanemupp@[...].se] 
# i want to replaxe the pattrn consonant o consonant, ie hoh ->  h, dad -
# >  d etc.
# so i have to check that the letter after the letter i am at is o and
# the next one is equal to the one i am at.

hi globalrev,

there are many ways.

best if you can play in irb,

"hoh" =~ /(.)o\1/
#=>  0

"testhoh" =~ /(.)o\1/
#=>  4

$1
#=>  "h"

if "testhoh".match(/(.)o\1/)
   "match!"
else
   "sorry"
end
#=>  "match!"

"qwxoxtyasdfzozghj".gsub(/(.)o\1/) do |m|
  p [m,$1,$~.pre_match,$~.post_match,$~.captures]
end
["xox", "x", "qw", "tyasdfzozghj", ["x"]]
["zoz", "z", "qwxoxtyasdf", "ghj", ["z"]]
#=>  "qwtyasdfghj"

"qwxoxtyasdfzozghj".gsub(/(.)o\1/) do |m|
  $1
end
#=>  "qwxtyasdfzghj"

"qwxoxtyasdfzozghj".gsub(/(.)o\1/) do |m|
  "<#$1> "
end
#=>  "qw<x>tyasdf<z>ghj"

"qwxoxtyasdfzozghj".gsub(/(.)o\1/){"<#$1> "}
#=>  "qw<x>tyasdf<z>ghj"

your next task now is to determine whether a certain char is a consonant regardless of case.

kind regards -botp