The error output indicates these are different threads, but I am aware that the process-to-thread relationship is like a parent-children relationship (one parent to many children). So these may or may not be separate processes.
Here is the output: 
USERNAME@COMPUTER C:\Users\USERNAME\eclipse-workspace\Project-X
# C:\Users\USERNAME\eclipse-workspace\WORKSPACE\dbi_test.pl
DBI is version 1.643, I am Pg, version of DBD::Pg is 3.10.4, server is
+ 120002
Name: dbname=db_name
Thread 1 running for A
Starting A under process id -6452
Thread 2 running for B
Starting B under process id -8912
Thread 3 running for F
DBD::Pg::db clone failed: handle 2 is owned by thread 33b7e8 not curre
+nt thread 3f29dc8 (handles can't be shared between threads and your d
+river may need a CLONE method added) at C:\Users\USERNAME\eclipse-wor
+kspace\WORKSPACE\dbi_test.pl line 297.
DBI is version 1.643, I am Pg, version of DBD::Pg is 3.10.4, server is
+ 120002
DBD::Pg::db FETCH failed: handle 2 is owned by thread 33b7e8 not curre
+nt thread 36a1cd8 (handles can't be shared between threads and your d
+river may need a CLONE method added) at C:\Users\USERNAME\eclipse-wor
+kspace\WORKSPACE\dbi_test.pl line 281.
Starting F under process id -8840
Thread 4 running for M
DBD::Pg::db clone failed: handle 2 is owned by thread 33b7e8 not curre
+nt thread 59f55b8 (handles can't be shared between threads and your d
+river may need a CLONE method added) at C:\Users\USERNAME\eclipse-wor
+kspace\WORKSPACE\dbi_test.pl line 297.
Starting M under process id -9280
Thread 5 running for S
DBD::Pg::db clone failed: handle 2 is owned by thread 33b7e8 not curre
+nt thread 5d7ed18 (handles can't be shared between threads and your d
+river may need a CLONE method added) at C:\Users\USERNAME\eclipse-wor
+kspace\WORKSPACE\dbi_test.pl line 297.
Starting S under process id -10640
$optimization->wait_all_children() is waiting...
DBD::Pg::db clone failed: handle 2 is owned by thread 33b7e8 not curre
+nt thread 5d7b358 (handles can't be shared between threads and your d
+river may need a CLONE method added) at C:\Users\USERNAME\eclipse-wor
+kspace\WORKSPACE\dbi_test.pl line 297.
Can't call method "finish" on an undefined value at C:\Users\USERNAME\
+eclipse-workspace\WORKSPACE\dbi_test.pl line 126.

USERNAME@COMPUTER C:\Users\USERNAME\eclipse-workspace\Project-X
#

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In reply to Re^2: Can't get multiple Parallel::ForkManager threads connecting to DBD::Pg database by perlygapes
in thread Can't get multiple Parallel::ForkManager threads connecting to DBD::Pg database by perlygapes

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