Re: Using regex to match double letters, and only double letters

You need to use capturing parentheses, and then backreference. EG:

#!/usr/bin/perl -w
use strict;

while (<DATA>) {
    next if ($_ !~ /([A-Za-z])\1/);
    print;
}

__DATA__
balloon
hello
world
foo
bar
perlmonks
merry
christmas
[download]

Which gives:

balloon
hello
foo
merry
[download]

See perlre for more information.

Hope this helps,
Darren :)

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Re^2: Using regex to match double letters, and only double letters by kwaping (Priest) on Dec 30, 2005 at 02:51 UTC
Good solution! I couldn't help but golf it a little. :) `#!/usr/bin/perl -w use strict; while (<DATA>) { print if (/([a-z])\1/i); } __DATA__ balloon hello world foo bar perlmonks merry christmas` [download]	[reply] [d/l]
Re^2: Using regex to match double letters, and only double letters by Anonymous Monk on Dec 30, 2005 at 02:07 UTC
That helps immensely, thank you very much indeed. Why I didn't think of that, I shall never know.	[reply]
Re^3: Using regex to match double letters, and only double letters by aquarium (Curate) on Dec 30, 2005 at 02:51 UTC
deleted the hardest line to type correctly is: stty erase ^H	[reply]
Re^4: Using regex to match double letters, and only double letters by kwaping (Priest) on Dec 30, 2005 at 02:54 UTC
That will give you two letters, but not two doubled letters (aa, bb, cc, etc.). I think you just misunderstood the OP.	[reply]