#!/usr/bin/perl

# LISTS...
@list = (1,2,3,4);
@list = reverse(@list);
# result: @list = (4,3,2,1)


# HASHES...
# because of the way hashes flatten into lists sometimes, reverse can
# also be used to invert a hash table, assuming the values are all unique.
%myhash = (1 => 5,
           2 => 10,
           3 => 15,
           4 => 20);
%myhash = reverse(%myhash);
# result: %myhash = (5=>1, 10=>2, 15=>3, 20=>4);


# AND SCALARS...
$x = "flinch";
$x = reverse( $x );
# result: $x  = "hcnilf"


# A ROUTINE...
# here is a subroutine that will reverse lines as you type them, or
# maybe you could use it on the command line if this file were saved as reverse.pl:
#     % cat myfile.txt | reverse.pl
&reverse_cat();

sub reverse_cat() {
    my( $line );
    while( $line = <STDIN> ) {
        chomp( $line );
        $line = reverse( $line );
        print "$line\n";
    }
}