G'day dirtdog,

"The objective is to return the unique values in the {108: tag."

The data you've identified as being the unique values (8480963411 and 8481963413) are not unique: both occur twice. Unfortunately, that raises questions about whether: your spec is incorrect; the wrong input data was presented; the expected output was wrong; and so on.

This gets the expected values you've identified into a shell variable using a one-liner with the input data you've shown.

$ echo $PM_1225496

$ PM_1225496=`perl -Mstrict -Mwarnings -ne 'BEGIN { $/ = "{S:{CON:}}" 
+} while (/^.*?\{108\:(\w+)\}\}.*$/g) { print "$1\n" }'`
{1:6392495900}{4:{177:1807300738}{451:1}{405:K22005}{108:8480963411}}{
+1:6392495900}{2:IVSN}{3:{108:8480963411}}{5:{MAC:00000000}{CHK:9F11}}
+{S:{CON:}}${1:6392495903}{4:{177:1807300738}{451:1}{405:K22005}{108:8
+481963413}}{1:6392495903}{2:IVSN}{3:{108:8481963413}}{5:{MAC:00000000
+}{CHK:12846}}{S:{CON:}}
$ echo $PM_1225496
8480963411 8481963413
$
[download]

I'll leave you to decide if that's what you wanted.