Hold Space

16

Heading translation

Strategy:

Let $held be the previously read line

Read lines one at a time

If the current line is an underline, print uc $held and discard it

Otherwise, print $held and store the current line in $held

At the end of the file, print $held if there is one

In one of the "P" languages, this is not too hard:

        #!/usr/bin/perl
        
        while (<>) {
          if (/^(.)\1+$/ && defined($held) && length($_) == length($held)) {
            # It's an underline
            print uc($held);
            undef $held;
          } else {
            print $held if defined $held;
            $held = $_;
          }
        }
        print $held if defined $held;

Not the loveliest code, but it is fairly straightforward