in reply to substitution in regular expression

You've placed code (push(@dic,$1);) inside the replacement part of the regular expression. Each three-letter code will be replaced by the string "push(@dic,$1);" instead of the code being executed, and because of that the string will never get shorter. Even though you could get the code to execute by adding the /e modifier on the regex, it still wouldn't do what you want (since the replacement value would be the return value of the push call), and so it's better to just move that code outside the regular expression.

Since you're matching three letters with your regular expression, and you want to replace those with the last two of those three letters, it's easier to just write it that way:

    while(length($line)>2){
        $line =~ s/([A-Z]([A-Z]{2}))/$2/;
        push(@dic, $1);
    }

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I'm sure other monks will have (TI)MTOWTDI and more elegant solutions, but the above gets what you want with only a few changes.

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Re^2: substitution in regular experssion
by aeqr (Novice) on Apr 23, 2014 at 20:04 UTC
    Thanks for the info, I have tried your solution but it doesn't seem to work :/

    Also I would like to know the way to do it without the while loop. That is, editing the string and saving as I have described...

[reply]
      ... it doesn't seem to work :/

      But what does that mean? In general, replies along the lines of "it doesn't work" are not helpful. How does it "not work"?

[reply]

      It seems you've edited your node to remove the while loop you originally had. Please don't do that without marking your updates because it confuses things, now monks won't know which version of your question to answer.

      ... it doesn't seem to work

      In what way? Do you get an error, or are you seeing unexpected results? Because it works for me:

      use Data::Dumper;
print Dumper([build_dictionnary()]);

sub build_dictionnary{
    my $line="ABCDEF";
    my @dic;
    while(length($line)>2){
        $line =~ s/([A-Z]([A-Z]{2}))/$2/;
        push(@dic, $1);
    }
    return @dic;
}

# Output (whitespace compressed):
# $VAR1 = [ 'ABC', 'BCD', 'CDE', 'DEF' ];

      [download]
      I would like to know the way to do it without the while loop.

      Why?

[reply]
[d/l]
        Sorry I made a mistake, yes it works indeed thanks. I wanted to do it without the while in order to train myself to use the global option and in order to do it in one line. Maybe not very useful but in my assignment it is recommended to find short solutions.
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