We have a regex tutorial at http://tutorial.regex.uk.

This module just provides an overview of the key type on which the regex package is built. You will need to import one of the API modules of which there is a choice which will depend upon two factors:

• Which flavour of regular expression do you want to use? If you want Posix flavour REs then you want the TDFA modules, otherwise its PCRE for Perl-style REs.
• What type of text do you want to match: (slow) Strings, ByteString, ByteString.Lazy, Text, Text.Lazy or the anachronistic Seq Char or indeed a good old-fashioned polymorphic operators?

While we aim to provide all combinations of these choices, some of them are currently not available. In the regex package we have:

• Text.RE.TDFA
• Text.RE.TDFA.ByteString
• Text.RE.TDFA.ByteString.Lazy
• Text.RE.TDFA.RE
• Text.RE.TDFA.Sequence
• Text.RE.TDFA.String
• Text.RE.TDFA.Text
• Text.RE.TDFA.Text.Lazy

The PCRE modules are contained in the separate regex-with-pcre package:

• Text.RE.PCRE
• Text.RE.PCRE.ByteString
• Text.RE.PCRE.ByteString.Lazy
• Text.RE.PCRE.RE
• Text.RE.PCRE.Sequence
• Text.RE.PCRE.String

The traditional =~ and =~~ operators are exported by the above API module, but we recommend that you use the two new operators, especially if you are not familiar with the old operators. We have:

• txt ?=~ re searches for a single match yielding a value of type Match a where a is the type of the text you are searching.
• txt *=~ re searches for all non-overlapping matches in txt, returning a value of type Matches a.

The remainder of this module outlines these Matches and Match result types. Only an outline is given here. For more details see the Matches and Match modules.