This will probably work, depending on what pattern1 and pattern2 really are: 
/
   pattern1
   (?:(?!pattern1).)*
   pattern2
   (?:(?!pattern1).)*
   pattern1
/x

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In reply to Re: How can I build regexp with "not" assertion? by ikegami
in thread How can I build regexp with "not" assertion? by putnik

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