Maybe a regex substitute would be faster, if you know the delimiter won't appear in the array. Something like:

foreach (@$arry) {
    my $x = join("\n", @$_);
    $x =~ s/^${from}$/${to}/mg;
    @$_ = split("\n", $x);
}
[download]

Also, if you're just modifying the array in-place, map is inefficient because it accumaltes the results into an array.