tphyahoo:
So the core question (speaking as a perler) is how do you write
my $s= 'abcdefg'; $s =~ s/a/z/g; $s =~ s/b/y/g; print "$s\n";
Simple patterns like this you'd just use a 'map' of course: main = print (clean "abcdefg") clean = map (by . az) where by c = if c == 'b' then 'y' else c az c = if c == 'a' then 'z' else c Running this: $ runhaskell A.hs "zycdefg" Now, using regexes instead we can get by with just the regex-compat lib, providing: import Text.Regex I usually flip the arguments to subRegex, since they're in the wrong order for composition (anyone else noticed this?): sub re y s = subRegex re s y regex = mkRegex Now , using proper regexes, we can write: main = print (clean "abcdefg") clean = sub (regex "b") "y" . sub (regex "a") "z" Running this: $ runhaskell A.hs "zycdefg" Similar results will be achieved with the other regex-* packages: http://haskell.org/haskellwiki/Libraries_and_tools/Compiler_tools#Regular_ex... I think TRE might be preferred for high performance cases. -- Don