TEST1 is supposed to match entries with BOTH EXT and INT curly delimiters update: so it SHOULD capture 2 matches in Dataline 1 but (per testing and hash contents) it is capturing only the first match in DataLine 1 -- SEE note 2. It correctly captures a single match in DataLine2

NOTE 1: regex in extended format & commented is update in the readmore (was referenced to ww's scratchpad)

NOTE 2: IF this is modified with an initial .* before the capture, the "{three 1 1 {...} {...}}" matches

#!C:/perl/bin -w
use strict;
use Data::Dumper::Simple;
use vars qw ( $i $j $tmp $test @data @found $found %h );
 
$i = 1;     # tracking counter - in full version does NOT necessarily 
+== $j
$j = 0;     # track datalines
%h = (); 
 
while (<DATA>)
   {
      push @data,$_ ;
   }

foreach $test(@data)
   { 
      test1($test);
   } 
 
&hashprint;
exit();
################ subs #############
 
sub test1 {
                  # first, get rid of previous array conents (needed i
+n full vers)
undef(@found);    # Categorized Q&A book answer; "@found = ();" is an 
+alternate
$j++; 
print "\n\t ***** STARTING dataline $j ****\n\n";
 
if ($test =~ /(\{{1}[a-z]{4,5}\s\d\s\d\s[^}]+?\}\s\{[^}]+?\}{2})/gx ) 
+ # see NOTE1
      {
        if ( $1 )
           { 
            $tmp = "\t\$j" . $j . "\$i". $i . ": " . $1 . "\n";
            push @found, $tmp;
            &hashify;
 
            print "TEST1 regex, dataline $j found match(es)\n";
            print "\t $1\n";
           }
           else 
           {
           print "\t TEST1 dataline $j, NO matches.\n";
           }
      } 
$i++;
return($i)
}
# end sub test1
# (more similar tests here in full version)
##############
 
sub hashify { 
$h {'datalinej'.$j."_i".$i} {"j".$j."i" .$i} = "@found"; # get all @fo
+und's elements into hash ???
$tmp = '';
return();
} 
# end hashify
###########
 
sub hashprint { 
print "\n\t\t~~~~~~~~~~~~~~~~ Dumping hash (HoA)\n";
print Dumper (%h);
print "\t\t~~~~~~~~~~~~~~~~ ending dump\n";
} 
# end sub hashprint and end subs
__DATA__
DataLine1 {error 1 1 {^E 0-20-9:0-50-9:0-50-9.*$} {^E 0-20-9:0-50-9:0-
+50-9.*$}} {three 1 1 {^.*35=A.*$|^.*35=5.*$} {^.*35=A.*$|^.*35=5.*$}}
+ {fixv 1 1 ^.*VFIXFxProxy.*Disconnected ^.*VFIXFxProxy.*Disconnected}
DataLine2 error 1 1 {^E 0-20-9:0-50-9:0-50-9.*$} {^E 0-20-9:0-50-9:0-5
+0-9.*$} {three 1 1 {^.*35=A.*$|^.*35=5.*$} {^.*35=A.*$|^.*35=5.*$}} {
+fixv 1 1 ^.*VFIXFxProxy.*Disconnected ^.*VFIXFxProxy.*Disconnected}
[download]

         ***** STARTING dataline 1 ****

TEST1 regex, dataline 1 found match(es)
         {error 1 1 {^E 0-20-9:0-50-9:0-50-9.*$} {^E 0-20-9:0-50-9:0-5
+0-9.*$}}

         ***** STARTING dataline 2 ****

TEST1 regex, dataline 2 found match(es)
         {three 1 1 {^.*35=A.*$|^.*35=5.*$} {^.*35=A.*$|^.*35=5.*$}}

                ~~~~~~~~~~~~~~~~ Dumping hash (HoA)
%h = (
       'datalinej1_i1' => {
                            'j1i1' => ' $j1$i1: {error 1 1 {^E 0-20-9:
+0-50-9:0-50-9.*$} {^E 0-20-9:0-50-9:0-50-9.*$}}
'
                          },
       'datalinej2_i2' => {
                            'j2i2' => ' $j2$i2: {three 1 1 {^.*35=A.*$
+|^.*35=5.*$} {^.*35=A.*$|^.*35=5.*$}}
'
                          }
     );
                ~~~~~~~~~~~~~~~~ ending dump
[download]

$test =~ /
      (                 # capture
      \{{1}             # SINGLE open curlybrace
      [a-z]{4,5}        # followed by 4 or 5 lowercase letters
      \s\d\s\d\s        # fol by whitespace, digit, whitespace, digit,
+ space
      [^}]+?            # fol by anything_not_a_closingcurly, one-or-m
+ore_times-but-as_few_as_poss
      \}\s\{            # closingcurly fol by whitespace fol by opencu
+rly (tween element 4 and element 5)
      [^}]+?            # fol by anything_not_a_closingcurly, one-or-m
+ore_times-but-as_few_as_poss
      \}{2}             # closingcurly twice
      )/gx;            # end capture, global, xtended syntax, end if_t
+est
[download]