Question

I’m Trying to sort letters in a file from A to Z
for example: a A B d r g
sorted: A a B d g r

@ARGV == 2 or die "Usage: $0 infile outfile\n";
open $old,  '<', $ARGV[0] or die $!;
open $new, '>', $ARGV[1] or die $!;
@mass=<$old>;
@array=qw(@mass);
@sort=sort @array;
@mass1=sort {uc $a cmp uc $b} @sort;
print $new @mass1;

Where am I going wrong?

Answer 1

I’m not sure what you intended to do with qw, but
suffice it to say that the contents of @mass will be never be used.

@array = qw(hello world);

Will cause @array to be defined to contain 2 strings, hello and world. It is just shorthand for:

@array = ('hello', 'world');

Which is why

@array=qw(@mass);

Evaluates to ('@mass') – an array with the single literal string of 5 characters @mass.

Maybe that’s what you’re doing wrong. What if you try

@array = map { split /\s+/} @mass;

@mass is the list of lines. Each line has words or just letters, separated by space.
What that last line does is maps each line with split /\s+/ – which will split each
line like 'ba ab a G' into a list like ('ba', 'ab', 'a', 'G') and @array will
become a single list of words/letters.

Then it’s a matter of how you want to sort them. See the other answer as well.

Oh, and remember to put back the spaces when you write out your file:

print $new (join " ", @mass1);

If you want each line to be sorted interdependently of the other, that’s easy too:

$mass1 = join "\n", map { join " ", sort (split /\s+/) }  @mass

That reads, ‘for every line in @mass, split on space, sort and join back again with space’, and with the resulting array, join with newline to produce the output of the file.

Note that you can drop in sort with a comparator like sort { $a cmp $b } etc.

If your file is too big, then looping is maybe prudent:

for my $mass (<$old>) {
    my $sorted_line = join " ", sort (split /\s+/, $mass);
    print $new "$sorted_line\n";
}