In your second snippet, you still print the last match of the last file, not the last match of each file.

This depends on what is in @completefile, as I previously discussed. I suppose it's also possible the OP wants just one result for all the elements of $exch, in which case the loop nesting should be reversed.

Then why did you proceed by putting the print in an if?

My point was that every iteration should output. If I didn't worry about using warnings, I could have had

foreach my $exch (@exch) {
    my ($su_adapter, $su_date);
    foreach (reverse @completefile) {
        last if ($su_adapter, $su_date) = /^.+\\(.+)_.+\..+?:(.+?)\s-\
+s(.+?)\s.+?\/$exch\s\|.+::(.*Up)\(\)/;
    }
    print "Results for $exch: $su_adapter, $su_date\n";
}
[download]

which reports the same info with no conditional.