use warnings;
use strict;
use feature qw(say);
# use diagnostics;

# say  zip ('ABCDEFGHIJ','abcde');

my $zipped= zip ('ABCDEFGHIJ','abcde');

say $zipped;

sub zip {
     # join "", sort {qq(\L$a) cmp qq(\L$b)} split "", $_[0].$_[1];
     join "", sort { lc $a cmp lc $b} split "", $_[0].$_[1];
}

__END__