my $text = "blah blah [click me](click me) more stuff\nblah [link here](link here) blah blah";
$text =~ s/(\[[^]]+]\()/$1\//g; # make links absolute
my @matches = $text =~ /(\[[^]]+]\(\/)([^\)]+)/g;
while (@matches) {
  my $part1 = shift @matches;
  my $part2 = shift @matches;
  my $orig_part2 = $part2;
  $part2 =~ s/ /-/g;
  $text =~ s/\Q$part1$orig_part2\E/$part1$part2/g;
}