But I was just wondering if there's a more Perlish way to do it that's not occurring to me?

This is one way to do exactly the same thing you are. I think it is a bit more "Perlish."

my $string = 'thisisatest'; 
for my $i (0 .. length($string)-2) { 
    (my $tmp = $string) =~ s/(.{$i})(.)(.)/$1$3$2/;
    print $tmp, "\n"; 
}
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-sauoq
"My two cents aren't worth a dime.";