Try this: 

#! perl -slw
use strict;

$/ = ''; # Paragraph mode

while (<DATA>) {
    if( /TEXT;\s+?LAYER 13[1-7];.+?STRING\s+(\S+)/s ) {
         print $1;
    }
    else{
         print "not found!\n";
    }
}

__DATA__
TEXT;
LAYER 133;
TEXTTYPE 0;
PRESENTATION 0,2,0;
STRANS 0,0,0;
XY 1;
X: 91410; Y: 50020;
STRING AVDD12;
ENDEL;

BOUNDARY;
LAYER 108;
DATATYPE 0;
XY 5;
X: 0; Y: 0;
X: 0; Y: 53530;
X: 91410; Y: 53530;
X: 91410; Y: 0;
X: 0; Y: 0;

[download]

Output:

C:\test>junk.pl
AVDD12;
not found!

[download]
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re: how to write multi-line regex by BrowserUk
in thread how to write multi-line regex by herman4016

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