perl: regex for matching after an optional character -


i need take string can have 1 of 4 formats:

  1. html
  2. text
  3. attachment
  4. email:[address]

i need regular expression correctly capture 2 things: $type, html, text, attachment, or email, , $arg, [address] if $type email, , undef otherwise. if $type not email, there should no matches @ all. i've written regex:

m/(html|email|text|attachment):?(.*)/;

which has problem match if there trailing text, html, or attachment, , match if there no :. so, instance, emailme@foo.com give ("email", "me@foo.com"). tried one:

m/(html)|(email):(.*)|(text)|(attachment)/;

which results in 5 groups. there way capture way want, no matches if there no colon after email, or if there colon after else?

yes, can use branch reset feature: (?|...|...|...)

/(?|(html)|(email):(.*)|(text)|(attachment))/

in branch reset, capture groups of each alternative have same numbers.

to exclude, "html", "text", "attachment" followed else (including colon), need condition on right (anchor, lookahead or other). same thing beginning.


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