Something else may be going wrong, as this works: 
#!/usr/bin/perl
use strict;
use warnings;
while (<DATA>) {
  print if /string1/../string2/;
}
close DATA;
1;
__DATA__
 this is string0 line
 and this is string1 line
 this might be string1a line
     and this line has string2
 to finish, string3 line ends it all

[download]
produces output 
 and this is string1 line
 this might be string1a line
     and this line has string2
Note that sometimes people use the __DATA__ feature to show file I/O related code. Please don't let that confuse you.

In reply to Re: find a string into an interval by shenme
in thread find a string into an interval by Anonymous Monk

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