1stline....pattern1.......pattern1.....
2ndline....pattern1.....pattern2...pattern1...
1a line....pattern1.......pattern1.....
2a line....pattern1........pattern2...pattern1.....


##</code><code>##

 
1stline....pattern1.......pattern1.....
2ndline....subst...
1a line....pattern1.......pattern1.....
2a line....subst.....

##</code><code>##

pattern1([^p][^a][^t]...[^1])*?pattern2([^p][^a][^t]...[^1])*?pattern1
pattern1.(pattern1){0}*?pattern2.(pattern1){0}*?pattern1