use warnings; use strict;
for my $i (
	"  ab ", 
	"  ab   ", 
	"  abc   ", 
	"  abcd   ", 
	"  abcde   ", 
	"  abcdef   ", 
	"  abcdefg   "
) {

##</code><code>##

	$i =~ /\A(\s*)(.*?)(\s*)\z/s or die;
	my $o;
	if (length($1) + length($2) < 6) {
		$o = substr($i, 0, 6);
	} elsif (length($2) < 6) {
		$o = substr($1 . $2, -6);
	} else {
		$o = substr($2, 0, 6);
	}

##</code><code>##

	printf "%-15s%s", qq("$i"), qq( => "$o"\n);
}
__END__