Perl String Modyifing

Question

Say I have a file called hello.txt which contains "Hello World!". If I wanted to make a script which opened the file and read the contents (I know how to do that) and added stuff to the string, how would I go about doing this?

For example: Hello World would have '..' inserted at the start of the string/content, and then every 2 characters later, except at the end. Also consider the contents will not always be "Hello World".

flesk · Accepted Answer · 2012-01-08 21:31:20Z

2

Since you already know how to read from a file, I take it your only real question is how to add .. after every 2 characters of any given string:

my $string = "Hello World";
$string =~ s/^|(..)(?!$)/$1../g;
print "$string\n";

Output:

..He..ll..o ..Wo..rl..d

Though I can't imagine how that would ever be useful.

The regex looks for the start of string or two characters not followed by the end of the string, using negative look-ahead, and replaces all matches with any captured characters followed by two periods.

edited Jan 8, 2012 at 21:31

answered Jan 8, 2012 at 21:26

flesk

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2 Comments

David G Over a year ago

Thank you a lot. One more question, say HelloWorld is all attached, this will output .. at the very end. Is there a way to prevent this?

flesk Over a year ago

@DavidG: I missed that part before I wrote my original answer. It's avoided with the negative look-ahead for the end of string added to my revised answer.

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