$ cat target-file.txt
Address1=
Address2=
Address3=

$ perl -Mstrict -wnle 'our @ports; BEGIN { my $source = "tcp 20 tcp 40 tcp 80"; @ports = $source =~ /tcp\s+(\d+)/g;} $_ .= shift(@ports); print' target-file.txt  > output.txt

$ cat output.txt
Address1=20
Address2=40
Address3=80

$ cat target-file.txt
Address1=
Address2=
Address3=