#! perl 
use strict;

my %data;
while( my $line = <DATA> ) {
    chomp $line;
    my $position = index( $line, ':', );
    my $key = substr( $line, 0, $position );
    my $value = substr( $line, $position + 1 );
    $data{ $key } = $value;
}
my @unsorted_keys = keys %data;
my @sorted_keys = sort @unsorted_keys;

for( my $index = 0; $index <= ( scalar( @sorted_keys ) - 1 ); $index++ ) {
    my $key = $sorted_keys[ $index ];
    my $value = $data{ $key };
    print "$key : $value\n";
}
__DATA__
a:1
b:2
c:3
d:4
e:5