in reply to parsing a multi-line pattern and replacing

If your file is XML or HTML, use a proper parser. For example, XML::XSH2: 
open inputfile ;
for //default set text() 'enabled' ;
save :b ;

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لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In Section Seekers of Perl Wisdom