Yes, yet another road to Rome!

I would have written the code very slightly differently.
(1) Rather than using $1,$2,$3, I would use list assignment of the variables. The match "worked" if the last one is "defined".
(2) A complex regex of the date/time is not needed
(3) In the substitution, I would use "|" as the separator to reduce the number of "leaning toothpicks" although some folks figure that this is a bad idea. mileage varies. 

#!/usr/bin/perl -w
use strict;

my @lines;
        
while (<DATA>) 
{            
   chomp;
   next if /^\s*$/;

   my ($date, $err_no, $err_msg) = 
       m{\[(.*)\]\s+\[(.*)\]\s+ERRORMSG\s+(.*)};
   
   if (defined $err_msg)  # the match "worked"!
   {                   
      push @lines, $date.' === '.$err_no.' === '.$err_msg."\n";
   }    
   else
   { 
      $lines[@lines-1] =~ s|\n$| $_\n|;
   } 
}      

print @lines;

=prints
2012/02/16 00:08:34 === 29 === unknown error Can't insert into price t
+able Please check Valueprice.pm line 52.
2012/02/16 00:08:34 === 39 === Invalid User
2012/02/16 00:14:52 === 105 === missing conversion rate
2012/02/16 00:14:52 === 29 === Can't use an undefined value as a HASH 
+reference at Value.pm line 77. 
=cut

__DATA__
[2012/02/16 00:08:34] [29] ERRORMSG unknown error Can't insert into pr
+ice table
Please check
Valueprice.pm line 52.
[2012/02/16 00:08:34] [39] ERRORMSG Invalid User
[2012/02/16 00:14:52] [105] ERRORMSG missing conversion rate
[2012/02/16 00:14:52] [29] ERRORMSG Can't use an undefined value as a 
+HASH reference at Value.pm line 77.

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In reply to Re^2: Not able to capture information by Marshall
in thread Not able to capture information by Anonymous Monk

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