Sure, how about

my $str = "foo baa bzz";
print $str, $/;
$str =~ s< ([A-Za-z]) (?:\1)+ >($1)gx;
print $str, $/;

__output__

foo baa bzz
fo ba bz
[download]

See man perlre for more info on regular expressions in perl.
HTH

_________
broquaint