#!/usr/local/bin/perl -w
use strict;

my @arr;
while (<DATA>) {
    push @arr, $1 if m/^\.(\w+)/ .. m/^\t+\.\w+\W+(\w+)/;
};

print join " ", @arr;

__DATA__
.this is a line
	.and second is another line
.again, a line.
		.Yet another line