Using Raku (formerly known as Perl_6)

raku -ne 'join( "\t", .words[0..*-3], .words[*-1] // "", .words[*-2] // "").trim-leading.put ;' 

Basically, the code above creates a list of whitespace-separated elements (words) in the desired order (last two elements switched). The elements are joined with \t tab, any leading whitespace is trimmed away with trim-leading, and the result is output.

Note, Raku's // defined-OR operator is used to avoid issues with Nil values in String context--an "" empty string is 'inserted' where necessary.

Sample Input (first line is blank):

A A B A B C A B C D A B C D E A B C D E F 

Sample Output (last two elements on each line are swapped--first line is still blank):

A B A A C B A B D C A B C E D A B C D F E 

https://docs.raku.org/routine/words
https://docs.raku.org/routine/join
https://raku.org

Using Raku (formerly known as Perl_6)

raku -ne 'join( "\t", .words[0..*-3], .words[*-1] // "", .words[*-2] // "").trim-leading.put ;' 

Basically, the code above creates a list of whitespace-separated elements (words) in the desired order (last two elements switched). The elements are joined with \t tab, any leading whitespace is trimmed away with trim-leading, and the result is output. This code works on tab-separated columns as well as on space-separated columns.

Note, Raku's // defined-OR operator is used to avoid issues with Nil values in String context--an "" empty string is 'inserted' where necessary.

Sample Input (first line is blank):

A A B A B C A B C D A B C D E A B C D E F 

Sample Output (last two elements on each line are swapped--first line is still blank):

A B A A C B A B D C A B C E D A B C D F E 

https://docs.raku.org/routine/words
https://docs.raku.org/routine/join
https://raku.org

Using Raku (formerly known as Perl_6)

raku -ne 'join( "\t", .words[0..*-3], .words[*-1] // "", .words[*-2] // "").trim-leading.put ;' 

Basically, the code above creates a list of whitespace-separated elements (words) in the desired order (last two elements switched). The elements are joined with \t tab, any leading whitespace is trimmed away with trim-leading, and the result is output.

Note, Raku's // defined-OR operator is used to avoid issues with Nil values in String context--an "" empty string is 'inserted' where necessary.

Sample Input (first line is blank):

A A B A B C A B C D A B C D E A B C D E F A B C D E F G A B C D E F G H A B C D E F G H I A B C D E F G H I J 

Sample Output (last two elements on each line are swapped--first line is still blank):

A B A A C B A B D C A B C E D A B C D F E A B C D E G F A B C D E F H G A B C D E F G I H A B C D E F G H J I 

https://docs.raku.org/routine/words
https://docs.raku.org/routine/join
https://raku.org

Using Raku (formerly known as Perl_6)

raku -ne 'join( "\t", .words[0..*-3], .words[*-1] // "", .words[*-2] // "").trim-leading.put ;' 

Basically, the code above creates a list of whitespace-separated elements (words) in the desired order (last two elements switched). The elements are joined with \t tab, any leading whitespace is trimmed away with trim-leading, and the result is output.

Note, Raku's // defined-OR operator is used to avoid issues with Nil values in String context--an "" empty string is 'inserted' where necessary.

Sample Input (first line is blank):

A A B A B C A B C D A B C D E A B C D E F 

Sample Output (last two elements on each line are swapped--first line is still blank):

A B A A C B A B D C A B C E D A B C D F E 

https://docs.raku.org/routine/words
https://docs.raku.org/routine/join
https://raku.org