That's no good. Your code is *way* too thick; a simple regex like that shouldn't really be worth commenting with such detail, but because your code is so condensed, they're necessary. And, whenever comments are needed with so short a snippet, its time to take a step back and wonder why.

When you need to perform a complex substitution, you should consider factoring out the code into a simple subroutine. It works wonders for readability; for instance, your example no longer needs comments, as the code is simple enough to explain itself. 

my $sentence = ( join " ", @ARGV ) ||
    "Give me a sentence containing kilometers or miles or both.\n" .
    qq|   Eg (note quotes): "I live 6 miles from here."|;

$sentence =~ s/\b (\d+(?:\.\d+)?) \s+ (kilometer|mile)/ transform($1,$
+2) /xige;

print $sentence, "\n";

sub transform($$) {
    my ($amnt, $type) = @_;
    my ($switched, $to, $one) = ($amnt * 0.63, 'mile');
    
    if ($type eq 'mile') {
        $switched = $amnt * 1.6;
        $to   = 'kilometer';
    }
    $one  = 's' if $amnt == 1;
    
    sprintf "%.1f %s%s", $switched, $to, $one;
}

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In reply to Re: mile/kilometer converter (category: stupid regex tricks) by jryan
in thread mile/kilometer converter (category: stupid regex tricks) by Your Mother

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