An excess of caution would suggest adding a defined test to the while-loop conditional. This test is not added by default by the compiler in the case of a complex conditional expression like the do-block:
    while ( defined($_ = do { ... }) ) { ... }

Yes, good practice does require the 'defined'. In this application, I am already assuming the format of a 'block'. The special case (block is defined, but evaluates to FALSE), which requires 'defined', should never happen.
Bill

Hello, Thanks a lot for your response and is working fine for the fixed format given before. Now I have a situation where I may get somehting like this

&LOG 
&LOG TEXT: "C:\temp\xyz.txt"
&LOG Action: DEFAULT 
&LOG Naming_Technique: DEFAULT_NAMING Default_Name: @ST/ABC1234/00001
&LOG Container: "current:entity"
&LOG Type: SIMILAR
&LOG Name: ABC-Y
&LOG Description: ABC-Z
&LOG Associated_Files_Directory: ""
&LOG 
&LOG TEXT: "C:\temp\PQR.txt"
&LOG Naming_Technique: USER_NAME Default_Name: @ST/ABC9999/00001
&LOG 
&LOG 
&LOG TEXT: "C:\temp\abc.txt"
&LOG Action: DEFAULT 
&LOG Naming_Technique: DEFAULT_NAMING Default_Name: @ST/ABC5678/00001
&LOG Container: "current:entity"
&LOG Type: SIMILAR
&LOG Name: EWQ-Y
&LOG Description: EWQ-Z
&LOG Associated_Files_Directory: ""
&LOG 
&LOG TEXT: "C:\temp\rtq.txt"
&LOG Action: DEFAULT 
&LOG Naming_Technique: DEFAULT_NAMING Default_Name: @ST/ABC2345/00002
&LOG Container: "current:entity"
&LOG Type: SIMILAR
&LOG Name: ERD-Y
&LOG Description: ERD-Z
&LOG Associated_Files_Directory: ""
&LOG
[download]

Here I do not want PQR.txt and its number ABC9999 in the output. Difference here is that, whenever I have USERNAME after Naming_Technique, i should avoid its .txt and number in the output. So my output remains same as before

[xyz.txt]
db_part_no=ABC1234
db_part_rev=00001

[abc.txt]
db_part_no=ABC5678
db_part_rev=00001

[rtq.txt]
db_part_no=ABC2345
db_part_rev=00002
[download]

could you please help?

Ahh, changing requirements in the middle of a contract - usually this requires a negotiation for more money :)

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11134376
use warnings;

{
local $/ = 'Associated_Files_Directory:';
while( <DATA> )
  {
  /TEXT:.*?([.\w]+)".*Naming_Technique:.*?(\w+).(\w+)\n/s and
    print $. > 1 && "\n", <<END;
[$1]
db_part_no=$2
db_part_rev=$3
END
  }
}

__DATA__
&LOG
&LOG TEXT: "C:\temp\xyz.txt"
&LOG Action: DEFAULT
&LOG Naming_Technique: DEFAULT_NAMING Default_Name: @ST/ABC1234/00001
&LOG Container: "current:entity"
&LOG Type: SIMILAR
&LOG Name: ABC-Y
&LOG Description: ABC-Z
&LOG Associated_Files_Directory: ""
&LOG
&LOG Part: "C:\temp\PQR.txt"
&LOG Naming_Technique: USER_NAME Default_Name: @ST/ABC9999/00001
&LOG
&LOG
&LOG TEXT: "C:\temp\abc.txt"
&LOG Action: DEFAULT
&LOG Naming_Technique: DEFAULT_NAMING Default_Name: @ST/ABC5678/00001
&LOG Container: "current:entity"
&LOG Type: SIMILAR
&LOG Name: EWQ-Y
&LOG Description: EWQ-Z
&LOG Associated_Files_Directory: ""
&LOG
&LOG TEXT: "C:\temp\rtq.txt"
&LOG Action: DEFAULT
&LOG Naming_Technique: DEFAULT_NAMING Default_Name: @ST/ABC2345/00002
&LOG Container: "current:entity"
&LOG Type: SIMILAR
&LOG Name: ERD-Y
&LOG Description: ERD-Z
&LOG Associated_Files_Directory: ""
&LOG
[download]

Outputs:

[xyz.txt]
db_part_no=ABC1234
db_part_rev=00001

[abc.txt]
db_part_no=ABC5678
db_part_rev=00001

[rtq.txt]
db_part_no=ABC2345
db_part_rev=00002
[download]

could you please help?

Sure. Which part are you having problems with?

---

🦛

I am sorry my mistake. Now I correct the input file.. The one with PQR.txt also starts with TEXT and not Part.

You are of course assuming that the Associated_Files_Directory field will always be equal to "" and that it will always be the last field in the record.