my proposition from the edit here works for me with your data:

  
  DB<132> p $x
<blah1 phase="2" type="MyType" more_keys="Values" <Unwanted/>  <SomeTa
+gIwant><k1="v1"></SomeTagIwant>

  DB<133> $re = qr/\btype="([^"]+)".+?<(\w+TagIwant\b|$)/


  DB<134> print join "|", $x =~ $re
MyType|SomeTagIwant

[download]

update
  DB<154> p $x
<blah1 phase="2" type="MyType" more_keys="Values" <Unwanted/>  <SomeTa
+gIwant><k1="v1"></SomeTagIwant>

  DB<155> p $y
<blah1 phase="2" type="MyType" more_keys="Values" <Unwanted/>


  DB<156> $re = qr/ \btype = "([^"]+)" .+?  (?: < ( \w+TagIwant)\b | $
+ ) /x


  DB<157> print join "|", $x =~ $re
MyType|SomeTagIwant

  DB<158> print join "|", $y =~ $re
MyType|

[download]

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!

In reply to Re^8: Regex Optional capture doesn't (solved !) by LanX
in thread Regex Optional capture doesn't by NetWallah

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