Re: What does \1 do?

Using a backslash "escapes" the following character. Given:

$n = "\1n\1r";

foreach (split //, $n) {
    print ++$x." ".ord($_)."\n";
}
[download]

...produces:

1 1

2 110

3 1

4 114

Check out Quote and Quote-like Operators in perlop.

C²

Comment on Re: What does \1 do? Download Code

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Re: Re: What does \1 do? by hv (Prior) on May 10, 2003 at 12:56 UTC
Using a backslash "escapes" the following character. That's not entirely true in this case: if the first character following a backslash is a digit `[0-7]`, the sequence of up to 3 octal digits following is the escape sequence, and the resulting octal number is converted to the character with that index: `perl -wle '$s = "\100"; print ord($s)' 64` [download] Similarly, "\x" introduces a sequence of up to 2 hex digits, eg "\x3f". In Unicode-aware perls (perl-5.6.0 and later) you can also introduce codepoints above 255 by putting braces around the hex number: `perl -wle '$s = "\x{1000}"; print ord($s)' 4096` [download] Hugo	[reply] [d/l] [select]

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Re: Re: What does \1 do?
by hv (Prior) on May 10, 2003 at 12:56 UTC

Using a backslash "escapes" the following character.

That's not entirely true in this case: if the first character following a backslash is a digit [0-7], the sequence of up to 3 octal digits following is the escape sequence, and the resulting octal number is converted to the character with that index:

  perl -wle '$s = "\100"; print ord($s)'
  64
[download]

Similarly, "\x" introduces a sequence of up to 2 hex digits, eg "\x3f". In Unicode-aware perls (perl-5.6.0 and later) you can also introduce codepoints above 255 by putting braces around the hex number:

  perl -wle '$s = "\x{1000}"; print ord($s)'
  4096
[download]

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