The join function takes a string and a list, producing a string with the first argument interpolated between all the list elements. If the list has one element there is no effect.

my @words = qw/Just another Perl hacker,/;
print join ' ..ubbada.. ', @words, $/;

__END__
Just ..ubbada.. another ..ubbada.. Perl ..ubbada.. hacker, ..ubbada..
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