I am also quite confused by your problem description and would like some example data, but since I need to kill a little time, I will try another reading. This may or may not be what you want:

/((.)(.)(.)(.)).*(\2\3\4.|\2\3.\5|\2.\4\5|.\3\4\5)/;
# You want either $& or $1/$6, I guess:
# print "($&)($1)($6)";
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The Sidhekin
print "Just another Perl ${\(trickster and hacker)},"